turning off the hinge box will operate the interlock, the chinge board is looking for the signal sent from the hinge board without that it kills the lift as it thinks the hinge is open, as you say the lift works when set as a non pvh, sounds like your issue is with the hinge system try changing the hinge board, also depending on the age of your lift? check the frequency of the both boards and remotes are the same? and if you have to leave the lift running without the hinge system/interlock working please lock the hinge down!
oh and I’m about to flood ebay with a shed load of stannah parts mainly remotes inc full 260 PVH set up’s 😉
