I managed to arrive at the solution when I tried to use vim with another user (root or a new one). The problem did not occur even though the ~/.vim folder was a symlink to that of the main user. In the end, the problem was that I had put this in my .bashrc file:

export TERM=linux

Removing it solved the problem.

The reason I had entered this parameter in .bashrc was because I noticed a strange behaviour in vim: in INSERT mode, pressing the ESC key and then an arrow key would insert the letters A, B, C or D, depending on the arrow key. As I use this key combination practically all the time when editing a file with vim, this was quite annoying. Investigating further, I discovered that the reason why this was happening was due to this vim plugin:

tmsvg/pear-tree

To cut it short by setting this parameter:

" Automatically map <BS>, <CR>, and <Esc>
let g:pear_tree_map_special_keys = 0 

in ~/.vim/plugin/pear-tree.vim solves the issue.