I'm wondering if the flap in your grinder is possibly stuck, twisted etc. I've heard you can push the flap back out of the way by sticking something up the chute. Do you clean the chute out? Maybe the flap is pushed out of the way some of the time, and sometimes it's not which causes the dense version of the grounds.

I recently took my 4 month old Vario apart and reversed the flap so that it's out of the way. My grinds have been super fluffy ever since. Not sure what's going to happen with static in the winter dry months, but so far it's fantastic.

Have you looked at this thread that describes how to reverse the flap?

Single Dosing My Baratza Vario Success!