I had the same issue last winter, and only with 2 of my mags (one was my fav. big stick).
Measured the mag bodies and they all were within spec. Thought that the cold weather
might have had an effect on my stippled grip.
Removed the grip and heated the inside with a hair dryer, wrapped one of the binding
tubes with paper, then inserted the tube into the grip. Allowed it to cool then repeated
it a couple more times. Have'nt had a sticking mag since!
Jim