(Bug report) Backspace deleting two characters at a time while typing in a post/comment body?

[XpeeN]

For over a month now, I noticed that if I try to delete a character (with either backspace or delete buttons) it'll delete 2 characters at a time. It seems that this bug coming from the markdown/BB editor, as when I disable it, it operate as expected. I'm using Firefox (Librewolf) on PC. Anyone else ran into this bug?

 

[pakalolo]

I can't find any reports of Xenforo bugs that match this.

 

[XpeeN]

I can't find any reports of Xenforo bugs that match this.

So apparently in troubleshoot (safe) mode it works as intended. I'll figure it out then. thanks.
Edit:
It was a weird interaction between a violentmokey's script and FC. cheers