can you tune the sensor settings on the 380 ?Don't know about the 550, but on the 380, the motion sensor for the parking capture is really sensitive.
Also I find that the videos captured while driving are mostly "Event" videos, not "Normal" ones. I have a feeling that the software doesn't compensate for normal gravity in the up/down plane, and so exceeds 1G at the slightest bump.
The DR550's settings are configured via the viewer with changes saved to a config file on the microSD card. The camera then reads this settings file at start-up.
The second page of the viewer allows you to fine tune the sensitivity settings that trigger an event recording in normal mode and a recording in parking mode. Too sensitive a setting and every pothole triggers an event. Too insensitive and a real bump may not trigger it. Advanced configuration allows you to review an event file that triggered the sensor and adjust the thresholds accordingly