Prohibit unintentional ~ from F6 button

Question

I have a mapping to remove trailing whitespace, defined like this: nnoremap <silent> <F6> :%s/\s\+$//<CR>''. It works fine, except that if I press Esc before pressing F6, instead of doing what it should it seems to do ~(switch case for character) for a bunch of characters where the cursor is placed.

How can I prevent that from happening?

EDIT 1:

I'm on Arch Linux latest updates as of 2017-04-28 with Vim 8.0, running in gnome-terminal. It's the same on all systems I've tested, but it's worth noting that I'm on a Swedish keyboard layout (EDIT: Just tested, and it's the same on en_US layout for me).

EDIT 2:

I've narrowed it down some. While F1–F4 are caught by my terminal (so can't say anything there), F5 produces 5 characters to switch case, F6 produces 7 characters to switch, F7 does 8 and F8 does 9. I've tried disabling my .vimrc, and that fixes the problem. I'll search through the config and report back when I find what caused it.

EDIT 3:

If I remove my .vimrc, Vi does it but Vim does not. What does that mean?

EDIT 4, major finding:

So I've found the line in my config that causes it. It's noremap <Esc><Esc> :noh<CR>. Still don't understand why, though. :/

Answer 1

The issue is caused by the line nnoremap <Esc><Esc> :noh<CR>, and can be fixed by changing it to nnoremap <Esc>a :noh<CR> or some other regular character instead of Esc. No idea why though.

Also, nvim seems to deal with <Esc> in the correct way.

Answer 2

Granted that I am running nvim and use Terminator, but for the very same purpose as described above I use: nnoremap <silent> <F5> :let _s=@/<Bar>:%s/\s\+$//e<Bar>:let @/=_s<Bar>:nohl<CR>. In order to isolate the matter I created a new .vimrc and added only the aforementioned line to the file. With both nvim (0.1.7) and Vim (8.0) I get the expected behavior (white space at end of line eliminated) and no characters changes case.

Edit: I changed to gnome-terminal, and the same appears there (i.e. everything work as expected).