Elite 6001 surgery table floor brake issue

Skytron made several brake versions. Three pistons with a spreader bar on the front (earlier models) four pistons (later versions) the fact that you have a dbl operating solenoid should be the latter. (There should be two hydraulic lines on each piston) Question: Do all the pistons not retract or just one / two? That would indicate a faulty piston. Assuming they all don't retract: Check that the down side of the solenoid actually energizes when you press the release button on the hand control. It is indicated by the plastic on the end of the solenoid changes color. If not replace that side of the solenoid. If that's ok and your check valves on both sides of the solenoids are good.(there should be four but may only have two depending on vintage) then remove the shuttle valve and look for corrosion which can be cleaned with very fine emery paper. Replace all and test. All that being said, I made the assumption that you checked the hand control to verify that the button is actually working. If you have another table swap the hand control and see if the problem resolves. Hope it helps.