Custom notification sounds reset when upgrading to Android 13

Question

We have an app with custom notification sounds. The app is already targeting Android 13 (using POST_NOTIFICATIONS and triggering the permission prompt on specific user actions). This all works well in itself.

We had two (out of two) cases where we got new devices with Android 13 (Pixel 7 Pro) and set them up by copying data from older devices (Android 11 and 12). What happened was this:

• We got a backup of the data of the app ✅
• We were not asked to accept notifications ✅
• All the notification channels had their sound were reset to the default Eureka sound 🤯

Why would the sounds be reset? And how can we avoid that?

We've never seen anything like this before when people have upgraded or gotten new phones. While notifications change a little bit each version of Android we've had pretty much the same custom sound stuff for more than a decade.

Clearing the app data let the app set up the channels just fine again. Also installing the app from Play Store and not getting any backup data works fine.

Edit: I just noticed that the Nest Doorbell app gave me the standard notification sound on my Pixel 7, instead of the standard ding dong sound. Clearing the app data made the app set up the notification channel with the correct sound.