if the door catches are anything like the 140 series, i know what is happening. there is the rail with the notches in in that the latch pin drops down on when latching. well, when you open the door, the mechanism lifts this pin or, actually its kind of a lever with a pointy part on the bottom that acts as the latch, and if it is cold out, this lever or pin can simply get stuck up in the latch, as the only thing pressing it back down is a small spring. I've opened my doors when its cold and have shut them and they've been like "bam!" and popped back open again from the bounce. i'll play with the pushbutton and i'll hear a small springy "click" and then the door will shut. thats the latch snapping back into place. i think this is caused by freezing moisture in the latch mechanism. a possible solution would be squirting lithium grease up there or using an oil can, remember: WD 40 is a penatrant, not a lubricant. use an actual lubricnat for these kinds of applications. also, doors can get stuck in the closed position, too. this is caused (as far as i can tell) by a dirty or sticky or unlubricated latch slide and latch. dab on lithium grease or wax and open and close a couple of times. that should cure it.
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'71 142S (parts), '71 144S, '74 164E