This is entirely abnormal.
Engine failing out may be due to air intake, easily though temporarily solved by bleeding the high pressure pump.
Air ingress will happen on that part of pipes where succion occurs. That is betzeen the tank and the low pressure fuel pump.
When I acquired my NC33 back in 2011 I suffered from comparable problem whenever sea was rough.
I found out monthes latter that fuel pipes where not 100% waterproof and air bubles could leak in.
This appeared due to filtering equipments (decanteur) that were a bit loose and their motions at rough seas put strains on the junctions and led to air intakes.
In the interim I mostly solved the problem by wrapping every nut or junction with autovulcanizing rubber.
From time to time I check that all those filtering elements are strongly tighgtened to their place.
Hope it helps,
Yves (Naïla, NC33 1978)