This seems to be the problem with code editor component as it also happens in its demo. I'd suggest to look around and ask on their issues page for fixes/recommendations.
Hi YellowAfterLife, thanks for the quick reply! I took a look at the issues page and saw that my first issue was already reported - and coincidentally, fixed fairly recently! https://github.com/ajaxorg/ace/issues/3943
Could you update GMEdit to use this updated commit? That should fix it - thanks so much!
That's a surprisingly small fix, you could even open keybinding-vim.js in GMEdit's directory, find that one line, and add "!" to the condition as in the commit.