Hi Bob you are spot on ,the rear brake discs are nearly new condition , after stripping them down
and looking very closely I noticed a shiner area on the bottom of the ridge , it was hard to see I spotted it only when I got my torch on it .
so I used my hand grinder to grind a small amount of metal away from the edge
fitted everything back together took it out for a test drive the car is now perfect.
I am thinking the rear brake disc being after market maybe the clearance between the
disc and the back plate is is not enough.