1997 Chevy Lumina front brakes locking up

A week & 1/2 ago my front brakes locked up with my wife driving. Both wheels were hot with a bit of somke and a foul smell. The shop the next day replaced both calipers and added bfl. Picked the car drove it home and all seemed fine. The day I go for a longer ride (golf) the car having a tough time going the car is dragging and I smell the same foul oder.
Needless to say the car is back in the shop and the Tech's aren't sure the problem really is. After to sets of both frt calipers I am at the same place I started. Tomoorow hopfully I will have the car back if they replace the right part. They belive that the brake master/ module is the problem.
I thought that maybe the hoses were collasping but they stated that they were able to bleed the caliper each time they had them off.
so here I sit. And wonder?

thanks Cary