That seems plausible. I can reliably reproduce the issue by syncing to AD, review a few cards and sync back to the desktop. I’ll open a bug report with the AnkiDroid folks directly.
It’s repaired. Dae, you were entirely right about the cause. Strangely, we saved it as string since 2014, don’t know why. Don’t know whether it was the actual used thing at some point in time. I assume python was tolerant enough to accept it, and a recent change, with rust probably, broke.
Anyway, it’s going to be put in a stable version soon, not waiting for the next big release (Thanks to mike for taking care of releasing )