This problem can be alignment or hydraulic, hence the following approach.
The fact multiple rebuilt calipers were installed and still had problem indicates the calipers are not the problem unless not correct for the vehicle or installed incorrectly (usually unlikely as other identical side is ok). Bent calipers can cause a similar problem, but the multiple new parts generally rule that out. The next item in alignment is the caliper mount on the strut, is it bent with respect to the spindle or does it have debris on the caliper mounting area? The next item for the hydraulics causing a drag is -if the pistons were pushed in and got some debris in the ABS unit, it could be causing this problem, however, disconnecting the caliper hose and seeing if gravity flows and pedal flow are ok would rule that out. If the car hit a curb or was hit, the bent strut assembly caliper mount or spindle may be your answer.