Well, this is my second puck of MWF. The first puck lasted several years, and spent about 9 months out of each year stored away in a drawer. During this period of storage, the puck would shrink, dry, and crack. No problem though, as a good overnight soaking before the first use each winter brought it right back to life. This at least the 3rd year for this puck, yet I never had this problem with it before. I can only explain it one of two ways: Each puck has a "shelf life", which may vary from puck to puck, or it's my brush. I've been using a Whipped Dog synthetic brush exclusively for the last year at least (love it), and I'm pretty sure I used it last year on this puck with no problem. I think I will pull out my old Semogue boar and go at it and see what happens. The quest continues!
If you continue to have issues with it you may want to try grating it and then press the shavings into whatever vessel you might choose. Maybe being hydrated then completely drying out for multiple cycles over time has hardened it and made it more difficult to lather.