Last year I got a fiber connection to my home (FTTH), and now I have internet and my phone running over this, using a FRITZ!Box 7390 modem/router. Everything works fine and the FRITZ is a very nice modem/router. However, when making long(er) telephone calls (typically over 10 minutes) my wife (I don’t phone that long;) experiences random disconnects. So, last night I had a look at this problem. Seems like more people experience this, and I also found a entry describing the problem at service.avm.de. It says a.o. that the problem would be resolved in the upcoming firmware upgrade. Now I was behind with my FW upgrades, so I decided to upgrade my FRITZ to FRITZ!OS 05.51, Firmware version: 84.05.51. First signs are promising. My wife did a 30+ minute telephone call, with no disconnects;)
Edit: Second test, this evening (may 29th) my wife phoned for over 1h15m, again with no disconnects. I’d say, mission success.