Intermittent snags like this have contributed to my loss of hair - and an increase in the daily intake of wine (it just hurts less after a few
!) But simplistically it is either fuel draining back to the tank (impossible I would have thought if it still happens with the fuel valve 'shut') OR it is air getting in. And the prime area would be on the upstream (suction) side of the EDP. Could the hose be old-ish, sharp bend and possibly porous when so bent? A Px check would prove or disprove this hypothosis.
Erratic starting in my experience has historically been an FCU malfuntion, but this would not be the case here if it has been changed. And anyway it doesn't always happen.............
Would be VERY interested to find out what the fault is when it is divined ~ VFR