Radio volume blasting after ending a phone call

I'm posting this question on behalf of my dad who is trying to solve this problem for my mom. She has a Kenwood ddx7ex installed in her 2005 Lexus. She likes the radio but whenever she hangs up from a Bluetooth phone call her radio kicks back on and the volume is blasting.

They have played with the volume offsets to no avail. She doesn't crank the volume during the call, she can be listening to the radio at one volume, take the call without touching the volume control and when she hangs up the radio will blast her ears off. Funny at first but now it's getting old.

Any info or ideas is greatly appreciated and my apologies if this isnt the right sub or place to post. Thanks