Hi Tom,
Thank you for reaching out. Over time microUSB ports in general tend to wear out a bit and the connection will become looser, especially with the movement and vibration those units experience in the vehicle. Typically swapping out the cable with one that has a firmer fit helps. We could try sending out a replacement cable from our inventory.
Other than that, perhaps try using something like this on the windshield to hold the power cable in place and prevent any pulling:
https://www.amazon.com/OHill-Organizer-Management-Organizing-Adhesive/dp/B071FXZBMV