Markdown editing : buttons black on black

Hi there
When writing a md file, the editor windows shows me the 2 buttons top right (close and “…” ) and the title “black on black” so I can’t see them …
right button md opening

For pdf files the opening widows is ok, I can see the 2 buttons on the right and the title white on black.
rigt button pdf opening
I hope wIth pictures,it’s better to understand (nx in french so “close” is “fermer” , “save” “enregistré” )

I tried to change the css but it doesn’t work
My nextcloud is 24.0.2 but it’s like that for a while …

Thank you for help and tell me how to fix it