Dashcam hardwire issue

[stooge]

No, the dashcam turns off around 10-15 seconds (quite consistently) after the ignition is turned off, even before the door is opened, so there is no footage of me getting out of the car and walking away

yeah i would say the dashcam hardwire kit is not connected properly at all.
the battery would not drop below 11.8 within 15 seconds unless it was totally forked, if it did i doubt it would start the vehicle.

dash cams have a super capacitor in them that keep the unit powered after you turn the vehicle off for about 15~30 seconds to allow it to shut down properly and not corrupt the memory/sdcard.
it sounds like your camera is just shutting down like normal when you turn the vehicle off which means the hardwire kit is not working to keep it powered in parking mode.