[Roadsters] Frozen rear brake adjuster

[Ronnie Day]

The pistons in the adjusting blocks are stuck. The adjusting bolts move
freely, both in and out, but the steel(?) pistons refuse to move. I took
one off and soaked it in PB Blaster overnight, but no change. Do I need to
hit them with heat?

The adjuster appears fine other that the fact the pistons won't budge. Am I
doing something incorrect?

Ron