I do not agree a voltage fluctuation between 12 and 14.5 volts would be the issue unless the antenna was that sensitive. I believe it is a software issue. I can isolate it very simply. After 3 to 5 minutes, it will start to studder. If I switch to anything else and immediately back to Bluetooth, it stops for another 3-5 minutes. So every song, I hit AUX, and back to Bluetooth and the song plays with no hesitation.
I don't have any stutter issues with my 8" system but there is a noticeable difference in sound quality. The sound,plugged into android auto, is much better than bluetooth connected to my Samsung Note 8 (running version 8)