I am using an Android car stereo that uses a PX6 processor and runs Oreo. It uses some kind of deep sleep that Poweramp doesn't seem to like. Poweramp will lose the album art of the last played song although the album art jpg was not deleted.
This is the scenario:
Album art displays just fine.
I turn off my truck and the radio goes to sleep (it doesn't completely shut down as it is ready to go a few seconds after starting the vehicle).
After a few hours I start my truck up. Poweramp is still on the same song, but the album art does not display.
I can swipe forward and back between songs, but the album art for the song that was active at vehicle turn-off is not displaying (all other album art is fine).
I can long press on the blank album art, select album art, and there is the album art ready for me to select chose. I am not connected to wifi so the art has been there the entire time.
The problem only seems to happen on the song that is showing/playing when I turn the vehicle off. After a few weeks, I wind up with a bunch of album art that doesn't display. The art is there and doesn't need to be downloaded again.... it just needs to be selected.