You can go into the relay screen in amber to see the relay logs or the complete amber logs in settings
A good way to debug this is also making the subscription inside nak in your computer
The since now in amber should not be a problem since it needs to connect first before replying to the nostrconnect
To know and fix those connection issues we would need more relays implementing the mute: keyword that fiatjaf created some months ago, this way we can implement some retry logic at the client and bunker side