When I first flew my LIV-P almost 25 years ago, after turning the master off, I could raise and lower the flaps 2 or 3 times before the pressure would bleed down enough to stop travel.
Over the last couple of years, however, that no longer happens--when I shut the master off, my flaps will lower if I put the handle down, but will not retract. I have replaced the "bomb" accumulator several times, without change. I have checked the flap linkage and there is no binding that I can find. The gear works perfectly.
My good friend and LNC2 driver Luke Alcorn has suggested that perhaps there is a sticking shuttle valve in the hydraulic pack (base upon the pack never having been opened or touched over the last 25 years. Does that sound like a winner? If so, how big a deal is it to remove that pack from a perfectly operating airplane (or can it be serviced in place)?