Why does my script restart by itself?

Scripting Forums AppleScript | Mac OS X
#1

I have this simple run-handler:

on run {}
	set caffeinatePid to do shell script "caffeinate -d > /dev/null 2>&1 & echo $!"
	set noLoops to 157
	do shell script "/opt/local/bin/brightness 0.05"
	start()
	do shell script "kill " & caffeinatePid
	do shell script "/Library/Python/3.9/bin/pb push done!"
end run

start() does all the heavy lifting. It exits cleanly and I have stepped through the following two lines, and when I do I see that after the last line the script starts over with the set caffeinatePid-line. Wot!?!?

I have executed this script for years without issues but (maybe) after upgrading to Tahoe it started to behave like this. I have ran it from Script Editor, Script Debugger and osascript, and it behaves the same everywhere.

#2

Please post start()
Hard to diagnose without it