This is a known issue, though not classed as a bug in my known bugs list. Server logs this as an error, but the script executes normally.
If you were to run this script in advanced's debugger, you'd find the same error code (101) returned when exit after last kicks the script out of the loop in FileMaker Pro as well. This is one of many "silent errors" currently returned in FileMaker scripts. ("Silent errors" are my term for errors that do not pop up a dialog to interrupt script execution when they occur.)
Aha, ok... I keep that in mind :) thanks