Can you help me defeat the stubbornly clumping salt in my new salt shaker?

My roommate recently received a set of salt and pepper shakers, and salt insists on clumping within a day of being put in the new shaker. We put rice in the shaker and moved it from the stove to the table, but the next morning, it was full of clumps once again. The shaker was not damp before we filled it, so that’s not the problem. It’s not humid here, and none of our other shakers clump at all. I’m beginning to think that we have a sentient salt shaker that hates being shaken, so it gets itself a tiny bit wet when we go to sleep at night in hopes that we will give up on using it.

My main questions are:
Why would the salt in one shaker consistently clump when the rest of the shakers are just fine?
How is it managing to clump so quickly? (I’ve never seen salt clump so quickly, even when it’s super humid.)
Why didn’t the rice help?
How can we get this shaker to work properly?
Is this shaker going to come after us in our sleep if we keep trying to make it be something it never wanted to be?