My modem router is powering down at random - twice yesterday, and once again this morning....in the middle of a football match!

I bought this device in November last year, and my internet connection has been very flakey. I had put this down to the nbn FTTN and rain getting in to the old copper cable. More recently I noted a pattern that the internet would drop about an hour in to a streamed football game, and then that it wasn't just the nbn line connection light that was flashing, but that all lights were out and the device was powering itself back up! I have found some reference to similar problems with Archer products in the past, and have upgraded the firmware and changed the placement of the device to ensure that it's not getting too hot (and it doesn't feel hot when I've noticed it powering up again).

Is there anything else I should be doing before taking it back for a refund?