I am using the original VIOFO's HK3 plugged into the camera directly (not on the GPS mount)
The parking mode is set to Auto event detection.
Parking mode motion detection and G-Sensor sensitivity are both set to highest. Do not confuse these settings with the other Motion detection and G-Sensor settings in the menus - these are dedicated to parking mode only.
I think VIOFO should also release a new version of the manual to explain the buffered parking mode and to guide users to properly set it up