4621 set on speaker fades in and out. Can I desensitize?

[MQH12]

I saw another thread that the OP did not seem to get answered and I have the same problem. If you tap on the desk the speaker goes whoop, if you put on the mute there is not a problem. Also I have changed the AGC on the phone.
Did this ever get resolved or any suggestions besides throwing away the phone. Let me know. Thank you in advance.

 

[JayNEC]

are you up to date on firmware?

 

[MQH12]

Oh forgot to say. It is 2.9 firmware, which I have heard has had direct problems. All of our phones are 2.9, but I dont hear about this from anyone else. Well they may have the problem, but they dont say anything or they dont notice it.