Not a good day...

Not being familiar with this model I can't be sure. Is there no bulkhead between the lazarette and engine room? Seems like a questionable design if (a) the garage platform sits so low that (b) backing down or passing traffic can crawl up and sufficiently fill the lazarette from that platform and (c) there is no protection from this influx of water to the engine room.

Do others who know the design think this is the basic chain of events here?

Would it be put down to a design fault .. if such things happen with ease .

cant' see the stern design on the pictures since the stern is partially sumberged.

on many boats (incl. smaller Az. ) the transom door opens directly into the ER, there is no separate lazarette. but with the swimplatform typically about a foot above the water line, it's hard to see a wake coming over the platform and sending enough water thru the door to cause a problem.

i've taken many wakes on the stern of the 70 footer i run and never had much water reaching th transom (no door though, ER access is from inside the boat). i've never gotten any significant water all the way to transom while backing down either.

Only design defect would be in the person who backs down hard or tows from astern with a transom door open and doesn't act with consideration of this being the result. How hard is it to close a door.

Well, first you have to be smarter than the door.

That would help.