Something like that. Forgot to take screenshot but it's pretty much accurate.
This always happens when it attempts to click on the transport candle at the end when you want to go out of AT after opening the chests. The popup confirmation window appears after clicking the candlestick but it errors probably when trying to click yes. Only the dwarf char gets this problem so I'm assuming it's related to it being a dwarf more than anything.
It's an unusual looking error but "IGF" means it's an error returned from the game from a RoMScript command. The only RoMScript command after clicking the candlestick is
Thanks for the suggestion, I'll do that the next time the char does AT.
I'm also gonna create another dwarf char (on another account to make sure it's not a case of bugged account) and see what happens if I let it do AT. Good thing AT level requirement is low so it will only cost me a few exp orbs to get it to the required level.
EDIT: Oh and to answer your question, no, there's no other popups open when the error appears.