For what my opinion is worth, as soon as an issue occurs, note the time on your watch (to the second) - having previously synched your watch to the modem. There'll be an hour's difference - don't bother with making your watch wrong on the hour!
Then we can see whether the T3.Sync loss occurs before or after the failure - becuae they can happen during the dark moments of modem reset.
The other thing you can do is to set the Thinkbroadband Quality graph running - and keep it running.
www.thinkbroaddband.com/ping This is a brilliabnt way of assessessing what's happening with your circuit.
Cheers