Loss of brakes after reversing

Sullivision

After I reverse and use the brakes wile reversing the brake, when I then go fowardthe brake peddle goes to the floor. Once I pump the braked a few times they return to normal. I replaced the pads, caliper brackets and pins at all four corners and this reduced the problem for a short period of time but a few thousand miles later and the problem is back.

Sullivision

Any Ideas of what mey be causing this would be greatly apreciated!