"SpamSieve - Set Category" could not be successfully executed.

Asked by a friend to look at a 26-inch iMac from circa 2010
OSX 10.10.3
Outlook 2011
Spamseive 2.9.30

On every message to be fetched via pop3, Outlook logs the following error:
While processing message XYZ (ID 12345), the rule “SpamSieve - Set Category” could not be successfully executed.
The AppleScript could not be found.
Error code -43

Reinstalled the applescripts, restarted Outlook to force a database rebuild (command-cntrl-click), killed off appleeventsd to make it forget pending events, all no help.
No clue as to WHICH applescript could not be found.
Is “Set Category” calling another script, or is there an issue finding that script itself?
Manual flag as spam and flag as not spam work fine, and behave as expected, moving the file to the proper directory in each case.

May buy a vowel?

I am neither a Mac Expert or familiar with Spamseive, but I expected more of a clue as to the issue here

Outlook is reporting an error finding the Set Category script itself. Perhaps it’s storing a reference to a file that has since been moved or deleted. Step 5e shows how you can re-select the proper script file.