Aftermarket Head + JBL amp = random audio loss/reduction

I have a 2010 Prius III (w/ JBL Premium Audio). I wanted to upgrade the head unit to get CarPlay, so I installed a Kenwood DDX6902, along with a TYTO-01 to interface with the amp and an AWSC-1 to interface with the steering wheel. It worked well for several months, however the sound signal is now completely erratic.

It sounds as if most of the energy is in the front left speakers, and doing a fader/balance check confirms that. However, occasionally the sound will cut to the rear speakers only. It doesn't seem to be a speaker connection issue, but perhaps that the amp isn't drawing enough power at times. One main reason for thinking this is that most all the time, as soon as I come to a stop and put the car in park, the audio kicks in full force on all speakers. Where should I start looking to find the source of the problem?​

 

Argh sorry, I meant head unit, not heads-up display. My brain don't work so good some times!

 

I don't recall doing that. I still have the factory so could probably reconfigure it that way if you think it would help. It's weird though that it would work for several months before acting erratically. Also, that doesn't seem to explain why I get full sound once I put it in park. Thanks for your reply!

 

Anyone else have any suggestions? If anything, could someone give me some potential reasons why I always get much more volume the instant I put the Prius in park?