Seems the problem would be resolved through hardwiring.
@jokiin has spoken about the problem of CanBus in the past. I've experienced issues with CanBus and systems tied together in past hardwires.
When I first hardwired my A129 Duo, everything was fine. But I couldn't figure out why every time I turned off camera and locked car, I kept coming back outside to see camera turned back on. Apparently, the 12V socket and the car alarm were tied to the same fuse, even though it wasn't mentioned in the manual.
Again, wired a family members car. Hooked into a benign fuse. But radio / infotainment had static. Odd. Changed fuse, went away.
Point here, a lot of systems are tied together. It appears the Start / Stop drops Voltage too low on the 12V socket to sustain the camera. I have Start / Stop and just hardwire. Can't say I've personally tested the 12V with a dash camera on my car, as I hate dangling wires. I have though used my phone as navigation and other stuff plugged in, and never had issue.
That being said:
1. Battery Pack ( as you mentioned)
2. Hardwiring
Are you two choices.