Rear Brakes get stuck
 

I have a problem with my rear brakes. For some reason the Handbrake adjust itself automatically, so after a while (2 days give or take), the Brake shoes get stuck. I already used other brake shoes and changed all Brake hardware in the back, but still the same problem. By the way this problem began just after the replacement of the axle seal (it had a leak) and because the old Shoes got wet with oil from the axle I had to replace them too.
How can I troubleshoot this problem?

Patrick