I have the same issue and it's very frustrating because I've tried changing so many settings (and restarting my phone) but just can't seem to eliminate it. I have a Samsung Note 10+ running Android 12 and OneUI 4.1; I have the paid version of Poweramp build 939. Here are a couple of examples of when I encounter this issue when I have both the Audible and Poweramp apps loaded:
(1) I'm listening to Audible on my BT headphones and turn the phone screen off; I click on my BT headphone to pause Audible, and then click again assuming Audible will restart -- but instead Poweramp starts playing.
(2) The issue also happens when the screen is on and I have the Samsung/Android notification bar pulled down -- I can see the Poweramp and Audible mini-players in the notification pulldown (they're "layered" over each other in that I need to swipe left/right to move from one to the other); I swipe to the Audible mini-player and press "Play" (using my finger) and Audible plays; I then click on my BT headset and the Audible player pauses; I again click on my BT headset, and instead of Audible playing, the mini-player automatically (i.e., by itself without me doing anything) "swipes" over to the Poweramp one and Poweramp starts playing ....
I love Poweramp but this issue makes it un-usable for me since I do a lot of my listening while I'm out walking, and so I need to be able to control my apps via my BT headset (phone is in my pocket with the screen off) -- all's good if I only want to listen to music via Poweramp, but I do frequently listen to my audiobooks and will often need to pause and un-pause (play) the audiobook (using my BT headset) while I'm out walking -- but this issue causes things to jump over to Poweramp as soon as I click on my BT headset.
Please advise what info you need from me to diagnose this situation. Thanks!