We have a Bluetooth LE setup with a medical watch which is paired to an Android phone using an authentication code. The setup works OK on most phones, but specifically on some Samsung Galaxy S21 models the device gets unpaired after using it for a few hours. Is this a known issue? We’ve tried to follow the HCI log file, and it seems that at some point the phone “forgets” the authentication code.

We expect the watch and device to stay paired until the user unpairs it manually.
The issue happens on 2 phones out of about 20 models we’ve tried so far, both phones are S21.
We’ve swapped watches with other test users for whom this doesn’t happen. We gave the users having those phones alternate phones to verify it is not something environmental. It is not.

We followed the HCI log and just looks like that at some point in time the phone “forgets” the watch.