Bug Changing selected text's colour also changes other text's colour

[Darkmaster006]

So I've found this extremely annoying bug that you can check here in this video:

cinnamon-20210827-2

Watch "cinnamon-20210827-2" on Streamable.

streamable.com

Basically, when I select some text to colour (I think this also happens with bold, etc.) other text, apart from the one selected, is changed.

EDIT: Another very weird example: cinnamon-20210827-3