That senerio tells me that the slider pins/assy. are frozen on allowing the outboard pad to continuiously ride the rotor. You apply the brake and it only half releases
Is there a dust boot over the slider assy? and, When you "greased" it, Was there greased slider parts visible for dirt to grab the grease? There shouldnt be.everything should be internaly greased/sealed.
This is just a statement.
Most people over grease things .
You may have a set of porely rebuilt calipers. I had two in a row the same day once.
Same side though but from the same place.
I always rebuildt my own after that treat of a time.
1.5 years of a slider assy. in the open weather, they will corode quicker than that.
Bottom line is:
The outboard pad is staying in the enguaged position, The only thing that can do that is the slider assy. OR the wrong caliper.