New Document defaults changing for unknown reason

Mac OS Sequoia, InDesign 2024 19.5.4

Every week or so, I find that when I go to create a new document, my default settings have changed. I am and have always been a US user, but regularly and without warning, new documents will be created as A4 with rulers set to millimeters, the dictionary set to UK: English, and paragraph composer set to World Ready Paragraph Composer. 

I've trashed preferences using the keyboard shortcut.

I've trashed the entire /Users/[me]/Library/Preferences/Adobe InDesign.

The problem still comes back.

I've found that trashing only the /Users/[me]/Library/Preferences/Adobe InDesign/Version 19.0/en_US/InDesign Defaults is enough to return to the correct US defaults. 

The problem still comes back.

Anybody ever seen anything like this? Any idea what might be changing my defaults?

I'm on a company-managed computer, so it may be some management thing they're running. But then again, none of my coworkers have had the same problem, so that seems unlikely.

I'm stumped.