Q: Problems with iPhone 7 audio source switching automatically

Related to the myriad telephone sound quality issues that are being reported, I'm experiencing the audio source changing randomly without my initiating it.  I'll start with the handset (where the volume often starts too low) and then will deliberately switch it to the speaker phone.  Randomly, it will switch back to the handset.  If my bluetooth is on, it may also try to switch to the handset on my home's cordless.   This is really annoying.  It seems the only stable source, ironically, is the lightning jack ear buds.