If the D7 bed has some slop in it (can be wiggled easily or if you see it flex a lot during the peeling process) then you may need to adjust the preload on the bearings that hold the bed bracket onto the z stage. The bracket has three bearings on the backside, two fixed that are aligned and a middle one that is offset that holds it on the other side of the rail. The middle bearing is an eccentric bearing that can be rotated to apply more side pressure and take out any play. The bearing has two setscrews that can be accessed from the front side once the bracket is removed (4 screws from the front). If you take the bearing block completely off and need to reassemble the z nut you can refer to this page.