Tonight I needed to replace 2 cracked cup washers on my rear brake caliper mount. I removed the caliper, sorted out the washers and then looked at the gap between the pads, checking it over which isn't a bad thing. One piston was extended further than the other and for some reason, I don't know why, but I pulled the lever so the gap closed and I couldn't get the rotor back in between the pads!
So I had to loosen the bleed screw, let some fluid out and then prise the pads back. Now I'll have to do a full bleed, maybe overhaul the whole system over the weekend as I can't ride it now.
I'm blaming tiredness!