Please add a logging functionality, so that even if something like that would happen in the future because of some special case bug, it would still be possible to figure out which subscriptions were removed.

Same thing happened to me, it seemed like it didn't do it when I had just two accounts, but it did do it when I had 3.

Not sure if it has anything to do with certain communities not being federated to the other instances

Here is everything I can remember doing:

1. Downloaded the apk

2. Installed and opened the program

3. Allowed notifications

4. Input my four instances: lemm.ee, sh.itjust.works, lemmy.basedcount.com, and lemmy.ml

5. Hit "sync" and watched them sync. Three of these instances had almost the same number of communities (around 120), but one had none whatsoever. It took two or three minutes for that instance (basedcount) to sync all of the communities, and in the end, it wasn't able to subscribe to about 20 of them for some reason. (maybe because nobody had ever gone to/searched for those communities from that instance before - I've heard this can lead to access problems, but you'd probably know more about that than I would)

6. About five minutes later, I got couple of notifications saying that 6(-ish) communities had been synced and that 18(-ish) had been unsubscribed across my instances. This confused me, so I checked my instance list and saw that all three of my instances with around 120 communities now had around 95.

7. I disabled notifications because they were starting to feel spammy.

8. I looked at the notification again and realized what had actually happened. I immediately uninstalled the program and resubscribed to as many communities as I could on lemm.ee, my main account.

Sorry this is so long - I hope it helps!