Microphone and earpiece not functioning in calls. Intermitten.

iPhone 4 GSM AT&T. I have already replaced the charging port once with an OEM part. It is not a service issue as it works perfect in another iPhone and I have switched SIM's and reprovisioned.

1) The microphone works 100% of the time in Voice Recorder.

2) Every now and then (about 1/3) when a call is made the speaker phone button will be white as if its already turned on.

When this happens, you cannot adjust volume in the call (press volume buttons and nothing appears). I have tried tapping the speakerphone button off and back on. No sound or microphone at all, doesn't matter if speaker on or off.

3) The other 2/3's the call is made fine and the microphone and earpiece work and the speakerphone button is not white as if turned on and the volume adjusts.

I'm thinking possibly noise cancelation microphone (power button flex?) or a software glitch. I have not tried a restore yet, only a update, just looking for some possible input.