Isn’t very helpful either… “errAEEventFailed”. I’d start by asking him to run a test script from Script editor. If that doesn’t work, then the system has issues. If it works, then it might be a TCC issue.
If you don’t care debugging with your user, you could have a test script, based on the one you showed above, that:
1: has “try”, “on error etxt number enum” and “end try” statements (“try” as the very first line and the others at the end, like in Xojo).
2: initialise a variable to count each line (or section), as you think is best.
3: in the “on error etxt number enum” statement, display a dialog showing etxt, enum and the last line number your code has set.
As in Xojo, you can then point out the offending line and start investigating from there, as the execution will jump directly to the “on error” handler when the problem occurs.