Delete Account script step error 213 but user does exist

Issue report by Jessica Reitz

Product

FileMaker Pro

Version

Advanced 13.0v1

Operating system version

Windows 7

Description of the issue

I'm needing some assistance in pinpointing where I'm going wrong. (this is surely operator error - not a FM bug. Hope I'm in the right place..) Any assistance or thoughts would be greatly appreciated.

Overview:
I'm getting scripting error 213 <no account matches that username> when I try to delete user accounts from other databases on the same server.

Details:
I have several files hosted on FMServer 13.
There is one "main" database in particular where a script resides to delete user accounts for a number of other databases.
The same user accounts exist for all databases, each user has the same password throughout all of them, including my full access account.
The "other" databases are all hosted on the same server, and have been authenticated through the "main" db's Manage External Data Sources dialog.
It produces error 213.

I tried running the script with "Run with Full Access" checkbox selected but there is no change. I did notice when running and debugging that Manage Security is not available until I hault the script. When the script stops, that access is available again.

(I thought I would be able to mark this as a question after I posted, but it seems I've posted in the wrong place.. Sorry about that...)