Rear brake woes

Hi all,
On the way home tonight my rear brake did the following:

  1. the pedal whent solid - and I could feel the drag from the rear brake.
  2. the pedal then went completely loose - all the way to the floor.
  3. after not using it for a while - it seemed to regain a little bit of braking ability - but nowhere near its normal function - it also felt like here was a little drag still - but need to check that later.

This was after quite a bit filtering.

I haven’t yet been able to investigate - by wanted to gather options on what to look for that might have caused this.

Check pads
Check pedal linkages /operation
Possible stone caught in calipers / linkage/pedal operation

Check pads, clean the piston and regrease it with RED grease.  Flush brake fluid and check lever level.