Fenix 5x sw13.3 sync to connect mobile fails first trial every time when having 4-5hour activity

After having more than 4 hours hiking activity (tracking every second) with fenix 5x, sync to connect mobile Android fails every time at first trial. If I reboot watch, sync succeeds. Does not fail when having less than 1.5 hour activities.

Is there some timeout with sync why it fails? Activity too long/big to sync?