Skin Glue coming off on ski base

After a tour, even when the skins feel pretty dry, I always hang them from a rack vertically and let them fully dry out for a day or so. Then I store them on the "skin saver" sheets. As others mentioned, it doesn't take much water (can even be un-noticeable) to screw up the glue.

So you dry them fully un-stuck?

I have the same issue as the OP. I always dry out my skins, but don't un-stick them before hand, so the glue side probably doesn't dry out as well.

Excellent thoughts here. I gave up on my Hi-5 (pomoca) skins after about a month and got the real thing (BD). Couldn't rely on them sticking for the third or fourth climb of the day when you have to climb out of the creek to the road and home. Even after regluing with BD glue! They hang out in my rig as loaners or if I forget to bring the BDs, which has happened.

So you dry them fully un-stuck? 

I have the same issue as the OP.  I always dry out my skins, but don't un-stick them before hand, so the glue side probably doesn't dry out as well.

yup, always unfold your skins so the glue is fully exposed to the air and let them hang dry for a few days before putting them into storage. Not letting the glue side dry out is the likely culprit for ending up with balled-up, mess-up glue that sticks to your ski bases.