Fridge/Freezer door opening while driving

From what you are describing it sounds like your seal has slightly compressed over the years. It sounds similar to my Norcold latch. Mine can be adjusted in or out. If you move the latch in it will put more spring in the plastic latch which makes it catch better. If your seal is compressed somewhat and a dollar bill slips out easily you can remove some plastic material from the base of the latch. I had to remove about .050 off the base of mine to get a tight seal. Also check to see if your return spring in the handle is in place and has not lost tension. When mine broke the door would shake open on ruff roads.