Errors with VImPlug

When I use VimPlug to manage my vim plugins, lh-cpp does not seem to work well
With a minimal vimrc file like below, there are lots of errors printed, see below.

Should it be configured differently when using vimplug?

call plug#begin('~/.vim/plugged')

Plug 'LucHermitte/lh-vim-lib'
"Plug 'LucHermitte/lh-style'
Plug 'LucHermitte/lh-tags'
Plug 'LucHermitte/lh-dev'
Plug 'LucHermitte/lh-brackets'
Plug 'LucHermitte/searchInRuntime'
Plug 'LucHermitte/mu-template'
Plug 'tomtom/stakeholders_vim'
Plug 'LucHermitte/alternate-lite'
Plug 'LucHermitte/lh-cpp'
"Plug 'LucHermitte/vim-refactor' " C++ refactoring
call plug#end()

[:] $ vim -u test.vim
Error detected while processing /home/eperson/.vim/plugged/lh-vim-lib/plugin/let.vim:
line 33:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_let")
line 34:
E10: \ should be followed by /, ? or &
line 35:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/lh-vim-lib/plugin/lh-project.vim:
line 20:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_lh_project")
line 21:
E10: \ should be followed by /, ? or &
line 22:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/lh-vim-lib/plugin/lhvl.vim:
line 29:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_lhvl")
line 30:
E10: \ should be followed by /, ? or &
line 31:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/lh-style/plugin/lh-style.vim:
line 18:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_lh_style")
line 19:
E10: \ should be followed by /, ? or &
line 20:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/lh-dev/plugin/add_import.vim:
line 26:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_add_import")
line 27:
E10: \ should be followed by /, ? or &
line 28:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/lh-dev/plugin/boundaries.vim:
line 18:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_boundaries")
line 19:
E10: \ should be followed by /, ? or &
line 20:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/lh-dev/plugin/dev.vim:
line 18:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_dev")
line 19:
E10: \ should be followed by /, ? or &
line 20:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/alternate-lite/plugin/alternate-lite.vim:
line 25:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_alternate_lite")
line 26:
E10: \ should be followed by /, ? or &
line 27:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/mu-template/after/plugin/mu-template.vim:
line 409:
E10: \ should be followed by /, ? or &
line 410:
E10: \ should be followed by /, ? or &
Press ENTER or type command to continue
[:] $ vim -u test.vim
Error detected while processing /home/eperson/.vim/plugged/lh-vim-lib/plugin/let.vim:
line 33:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_let")
line 34:
E10: \ should be followed by /, ? or &
line 35:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/lh-vim-lib/plugin/lh-project.vim:
line 20:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_lh_project")
line 21:
E10: \ should be followed by /, ? or &
line 22:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/lh-vim-lib/plugin/lhvl.vim:
line 29:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_lhvl")
line 30:
E10: \ should be followed by /, ? or &
line 31:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/lh-dev/plugin/add_import.vim:
line 26:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_add_import")
line 27:
E10: \ should be followed by /, ? or &
line 28:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/lh-dev/plugin/boundaries.vim:
line 18:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_boundaries")
line 19:
E10: \ should be followed by /, ? or &
line 20:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/lh-dev/plugin/dev.vim:
line 18:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_dev")
line 19:
E10: \ should be followed by /, ? or &
line 20:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/alternate-lite/plugin/alternate-lite.vim:
line 25:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_alternate_lite")
line 26:
E10: \ should be followed by /, ? or &
line 27:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/mu-template/after/plugin/mu-template.vim:
line 409:
E10: \ should be followed by /, ? or &
line 410:
E10: \ should be followed by /, ? or &
Press ENTER or type command to continue
[:] $
[:] $ vim -u test.vim
Error detected while processing /home/eperson/.vim/plugged/lh-vim-lib/plugin/let.vim:
line 33:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_let")
line 34:
E10: \ should be followed by /, ? or &
line 35:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/lh-vim-lib/plugin/lh-project.vim:
line 20:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_lh_project")
line 21:
E10: \ should be followed by /, ? or &
line 22:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/lh-vim-lib/plugin/lhvl.vim:
line 29:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_lhvl")
line 30:
E10: \ should be followed by /, ? or &
line 31:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/lh-dev/plugin/add_import.vim:
line 26:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_add_import")
line 27:
E10: \ should be followed by /, ? or &
line 28:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/lh-dev/plugin/boundaries.vim:
line 18:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_boundaries")
line 19:
E10: \ should be followed by /, ? or &
line 20:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/lh-dev/plugin/dev.vim:
line 18:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_dev")
line 19:
E10: \ should be followed by /, ? or &
line 20:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/alternate-lite/plugin/alternate-lite.vim:
line 25:
E110: Missing ')'
E15: Invalid expression: &cp || (exists("g:loaded_alternate_lite")
line 26:
E10: \ should be followed by /, ? or &
line 27:
E10: \ should be followed by /, ? or &
Error detected while processing /home/eperson/.vim/plugged/mu-template/after/plugin/mu-template.vim:
line 409:
E10: \ should be followed by /, ? or &
line 410:
E10: \ should be followed by /, ? or &
Press ENTER or type command to continue

Alternatively on my other machine I get these warnings:
Warning: While defining nmap <C-L><Ins> to <Plug>MarkersMark: there already exists another mapping starting as <C-L><Ins> to <C-W>l.
Warning: While defining vmap <C-L><Ins> to <Plug>MarkersMark: there already exists another mapping starting as <C-L><Ins> to <C-W>l.
Warning: Cannot define nmap <C-J> to <Plug>MarkersJumpF: a previous global mapping on <C-J> was defined in /home/eperson/.vimrc.
Warning: Cannot define vmap <C-J> to <Plug>MarkersJumpF: a previous global mapping on <C-J> was defined in /home/eperson/.vimrc.
Warning: While defining nmap <C-L><S-Del> to <Plug>MarkersJumpB: there already exists another mapping starting as <C-L><S-Del> to <C-W>l.
Warning: While defining vmap <C-L><S-Del> to <Plug>MarkersJumpB: there already exists another mapping starting as <C-L><S-Del> to <C-W>l.
Warning: While defining nmap <C-L>$ to <Plug>MarkersCloseAllAndJumpToLast: there already exists another mapping starting as <C-L>$ to <C-W>l.
Warning: While defining vmap <C-L>$ to <Plug>MarkersCloseAllAndJumpToLast: there already exists another mapping starting as <C-L>$ to <C-W>l.
Warning: While defining nmap <C-L><End> to <Plug>MarkersJumpOutside: there already exists another mapping starting as <C-L><End> to <C-W>l.
Warning: While defining smap <C-L><End> to <Plug>MarkersJumpOutside: there already exists another mapping starting as <C-L><End> to <C-W>l.
Warning: While defining xmap <C-L><End> to <Plug>MarkersJumpOutside: there already exists another mapping starting as <C-L><End> to <C-W>l.

[LucHermitte]

First error

It looks like continuation lines are disabled, or may be you're in compatible mode.

If you add the following in your .vimrc, you should be able to know in which situation you are.

echo &cp
echo &cpo

I'll see to fix my scripts more resilient, in the mean time, you should be able to add

set cpoptions-=C
set nocompatible

in your .vimrc to force Vim to be in a more flexible mode. It looks like a vim flavour compiled to be minimal and to stick as closely as possible to vernacular vi.

The warnings

This means, somewhere (vimrc, other plugin...), there is a mapping from <C-L><End> to <C-W>l. Because of this, lh-brackets mappings are disabled. You'll need to choose another keybinding and put it in your .vimrc.

See :h <Plug>MarkersJumpF

[LucHermitte]

The first error should have been taken care of. However, it's likely to just neutralizes all the plugins.
If you want to use lh-cpp (or any other plugin I maintain), don't be in compatible mode.