The issue is registered and filed by Microsoft as a bug. Attached is part of the answer of the support guy from MS:
"I will proceed with filing this bug internally. Once there is a change, I will notify you. At this point I have no timelines or anything that can be publicly shared."
Of course, when there is a feedback from Microsoft regarding this bug, I will share the info here
This is not a valid fix for the bug (which I experience too), as auto-sized columns themselves don't work. They often result in clipped text (...).
Both these problems are pretty much deal-breakers for us!
Interestingly, when you find yourself in the buggy situation (the matrix didn't refresh), 5 clicks on the very same slicer checkbox will ultimately get you back to the expected state. Go figure.