I have occasionally had weirdness like what you described, DEinspanjer. I think it's suction, like water frozen/adhering on the rubber window gasket...
@brianman, I've been thinking about how to respond to you without going into a lengthy lecture about experimental error, statistical error analysis,...
Going on a road trip with a gasoline car, you have to stop at a pump, wait 5 to 10 minutes while the car fills up, move to a parking spot, then go to...