Thank you for your advice.
I solved my problem in other ways. Here are the steps:
First, I kept deleting event sheets until I found the problematic event sheet.
Second, I deleted a certain 'Toggle disabled' JavaScript Action in the problematic event sheet, and the program ran normally, but there was no problem with that code.
Finally, I found that after this code block was toggle disabled, the group it belonged to was toggle disabled again.
This is the cause of the problem.
Just making sure all code blocks 'toggle disabled' are only done once solved my problem.