I have the following two mappings in my vimrc file
nnoremap <C-j> :tabp<CR>
nnoremap <C-k> :tabn<CR>
Ctrlk works, but Ctrlj lands me in insert mode for some reason. If I issue the command :nnoremap <C-j> :tabp<CR> then Ctrlj works correctly.
If I issue the command :map or :verbose map I see the mapping for <C-k> but nothing for <C-j>. Why is this happening?
A plugin, imaps.vim was interfering with the command, most likely unmaping it (thanks to Benoit for pointing it out). If this happens to anyone else, just delete the plugin.