ZTE Majesty (Z796C) internal mic disabled with headphones plugged in

[MadMax]

I have a ZTE Majesty Z796C phone on the straighttalk network (Verizon towers). The current android OS on it is 4.1.2.

When I first got this phone, I could plug it into a headphone adapter (audio cassette) so I could listen to MP3 music in my car. When someone called, the music would stop and I could talk to the person (I can hear them thru the car speakers) and they could hear me just fine. I noticed when in-call, the "speakerphone" button on the screen was greyed out so I could not select it.

However, recently when I was traveling and doing this, when a person calls they cannot hear me but I can hear them fine thru the car speakers. I noticed on the screen the speakerphone button is available to select now. But if I select it, the caller can be heard from the phone's speaker instead of thru the car radio's speakers.

I noticed with my cassette adapter or any set of regular headphones plugged into the phone, the icon that appears at the top of the screen is that of a headphone set with microphone - not just headphones icon.

Mechanical problem with the headphone jack on this phone or OS update causing the problem?

 

[Rukbat]

Unannounced new "feature". The philosophy probably being that if you have a headset plugged in during a phone call, it's a hands-free, and the phone's mic might be muffled in your pocket.