Replying in case it helps another lurking lemming one day:

I ended up replacing the tag with an OEM AirTag in the end.

I spoke with the manufacturers tech support, and they said they were not able to reproduce my issue.

After factory resetting it and replacing the battery multiple times, I was able to get it to load into find my again - but it stopped working again shortly afterwards…. Not at all worth the hassle.

Any idea how I can update the airtag if I can’t connect it to my phone? Trying to search for it in FindMy doesn’t pop up. Tried resetting it by pulling out the battery.

Found something online that says you can fully factory reset by pulling out the battery and reinserting it 10 times and it’ll beep 5 times instead of the normal 3 - I will try that when I get home tonight and will update this post if it works.

If that doesn’t work, any chance you know of anything else I should be checking?