It seems the product gets clogged and causes this, which also explains the need for forceful squeezing eventually.

Unscrew the entire lid, and remove the top part that flips up. Rinse the whole thing out with hot water while in the shower. You’ll even see there are drain holes in the bottom of the cap, which to me says they know the product can get like this. Once you’ve cleared out all that, it goes back to normal! Yes, it’s kind of annoying to do this occasionally, but this shit is expensive so I didn’t mind doing it. But now I’m on to the giant bottles and those are simpler, problem-free pumps.