Hello,
I'm running Questie 7.2.2 and I've had a problem with one quest each time I would advance the quest goal by 1, I would get an lua error in chat. This is the quest in question.
https://www.wowhead.com/wotlk/quest=11246/gruesome-but-necessary

I was sure I made a screenshot of the error in chat but I must have messed up so I can't show the exact error.

Hoping it's enough for you to fix/check.
Thanks

Definitely an issue but already fixed in #4186 with c1de598, should be included in a new version soon