@lfbrock Thanks for finding the underlying cause!
I didn't see the outstanding issue when I was browsing for it, and that explains the consistent behaviour we saw.
Sadly I won't have time until next year to get involved with this, unfortunately. We're otherwise prioritized in the office for the moment, and since we have a workaround for now, there was no hurry from the powers that be to allot time for me to do it soon.