Pu=strftime "en août" breaks fileencoding

On my French Windows 10 Pro laptop :language returns

Current language: "LC_COLLATE=fr_FR;LC_CTYPE=fr_FR;LC_MONETARY=fr_FR;LC_NUMERIC=C;LC_TIME=fr_FR"

In my $vimfiles/vim/enter/vimrc.vim I have

set encoding=utf-8

and my different filetypes have (:se fenc) fileencoding=utf-8.

So when I :pu=strftime('%A') I get a line below the cursor showing the weekday in French.

Here comes the problem, only in August: :pu=strftime('%B') opens a line below with the month in French, but not in August - oh no, what I get is ao<fb>t where that <fb> is some kind of holding character. So my first question is how to stop this?

Now for the additional problem, only in August: Of course I figured out that I could get rid of that holding character with :w followed by :e, and “Voila!”, that :put is fixed to août, which it should’ve been from the start, but “Wtf!” now fileencoding=latin1 and all my utf-8 glyph’s in that file have been un-undoably converted to latin1 combinations. So I could fix that with se fenc=utf8 followed by diff’ing against a previous version of the file, and went as far as to begin a function! FixConversionToLatin1() to repair that mess (in my $vfv/plugin/plugin.vim), but this is ridiculous - none of this happens mess happens in classic Vim. Something’s wrong with the Neovim implementation of strftime - any ideas?

pu=strftime “en août” breaks fileencoding #30013