Undo unavailable after play testing?

I am unable to undo any script edits after I play-test my group’s game. I don’t know if this is a problem for anyone else but it gets really annoying if I’m unable to undo an error I find.

Are you closing the entire script at the top? Closing it basically finalizes your changes and you can’t go back and edit them. Try keeping it open and just switching your tab to the place instead of closing it.

No, I keep the script tab open. It’s when I press play then undo becomes unavailable.