I know there is a solution to add a code snippet to turn visual text editor on from https://codex.bbpress.org/enable-visual-editor/
But do I paste that in the bbpress function.php file?
You would paste that code into your theme’s function file.
If you do not have a child theme you should consider creating one, just google “wordpress child theme video” and you’ll find lots of help. You’d then put this code into that theme’s function file.
If you put it in the main theme (or indeed bbpress) it will be overwriten by any upgrades to those.
it was a plugin issue, so weird….
With several thousand people writing plugins and all in theory choosing unique names for things like functions and variables, it’s not surprising that things clash occasionally !
Anyway – glad you’re fixed !