Solved? turns out the fault F1 is Watchdog card in the dash-display which looks forward for correct inputs then allows lift to operate. If watchdog times out for no apparent reason the this means the watchdog is faulty (F1) and must be replaced. However, managed to duplicate this fault by removing Fuse 1 while operating and also will display F1 if the line contactor is opened when operating. Suspect rough driving surface opens the line contactor contacts. More tests next week.
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