Ear speaker and mic not active/functional

Phone has not been damaged, dropped, or exposed to moisture. Suddenly I get no audio from the ear speaker and when making or answering a phone call the other end cannot hear me. Thing is, if I connect a headset/earbuds/mic then everything works fine. This makes me suspect that the phone thinks it *always* has an external headset connected, even when it does not. I have tried cold-booting the device, and connecting/disconnecting my headset to the jack, but the problem persists.

Also speakerphone works fine during calls. And the issue is not related to just phone calls, I can't get any audio out of the ear speaker.

If I open up the phone, is it possible I will find an issue with a physical connection at the 3.5mm jack? Has anyone else encountered this problem or maybe have a possible solution in mind?