The zipper-problem

I think I finally solved my zipper-problem.
Apply scientific-method = guile-and-cunning.
The zipper of my down winter jacket liked to be dysfunctional. Engaged, it wouldn’t zip.
I tried everything, trying to discern a position in which it would function.
My attempts were to fully engage the zipper-base in the starting-channel, but more than often it wouldn’t zip.
Prior experience with dysfunctional zippers noted the importance of fully-engaging the zipper-base, but that wasn’t working in this case.
Recently I noticed if the zipper-head was rotated counterclockwise it made the zipper work.
Apparently if not rotated the zipper-head doesn’t line up properly and jams. The zipper is thereby rendered dysfunctional.
Rotation isn’t much, perhaps four degrees.
It doesn’t like to rotate, which is why it’s only four degrees.
But apparently that’s enough to line up everything properly, and make it work.
So now I have to remember to rotate the zipper-head, as opposed to fully engaging the zipper-base; what I’m used to.