The last 3CX update has been annoying. I have upgraded 3 clients PBX to v.15.5 SP3 and what a mess. I upgraded then remotely on saturday morning. I tested one of then with a grandstream GXP2130 phone because I wanted to test CSTA. That feature worked correctly but I noticed that each time the phone was registered to the PBX it just started ringing till ring timeout. The phone showed on the screen it was being called by itself, from his own extension. The PBX was not aware of a call in progress. The GXP2130 phone had firmware version 184.108.40.206 which is the last stable one from grandstream and was working properly on 3CX v15.5 SP2 though lately it started showing the annoying not compatible firmware red warning which we had to explain to the client the best we could. I took captures on the phone and there were no invite messages at all. Maybe there is something on the 407 register challenge message reply from PBX that makes the phone start ringing. I updated the phone firmware to version 220.127.116.11 beta and the phone stopped doing that annoying thing. I didn't realize on that moment it was a PBX update issue. I just thought it could be because of the network where I was doing the remote tests through SBC. I thought about SIP ALG but it was disable on router. Anyway, I didn't pay to much attention to the problem on that moment. What an error! On sunday afternoon when I decided to take a look to one of the clients PBX I found out all GXP2130 phones on that office were showing ringing icon on the UI. A real headache to update those phones to stop that. And they were quite a few. I checked the other client which had a lot more phones. Again all phones ringing. I had to disable SIP service on 3CX and wait till phones lost registration because the phones were totally blocked. When ringing you can't change any configuration on grandstream phones. The phones on this two clients offices where upgraded to the firmware provided by 3CX 18.104.22.168. GXP2140 phones on firmware version 22.214.171.124 were not affected by this problem nor the one I had upgraded to 126.96.36.199 beta version. But today I had upgraded some GXP2140 phones on my office to the firmware 188.8.131.52 provided by 3CX and same ringing problem that happens with version 184.108.40.206 on GXP2130 phones appeared. It doesn't happen so often on these phones but it happens. Any clue of what is going on. Any configuration I have to change? Very very very very very annoying updated. Very upset. The more I work on VoIP the more I'm disappointed with providers. When there is not a PBX bug, there is a trunk provider problem, a phone firmware bug, ... If you don't upgrade there are bugs, if you upgrade some are solved but others added. I would really appreciate more stability no matter if upgrades come at a slower pace. Sorry the large message.