There is a possibility of a short-circuit causing an engine shutdown. Apparently, there is a known fault whereby a short can result in the FADEC "fail-safing" to engine shutdown, and this is one of the competing theories as the wiring apparently runs near a number of points in the aircraft with water (which is a really odd design choice).
Now, I'm not going to sit here and tell you that (a) the wiring actually runs there (the wiring block diagrams are easy to find, but block diagrams don't show actual wiring paths), (b) that there is anything to indicate that water could reach such wiring in a way that could cause a short, or (c) that it actually did so. I don't have that kind of information.
All I can tell you, at this point, is that aviation experts are saying that a short at such a location would cause an engine shutdown and that Boeing was aware of this risk.
I will leave it to the experts to debate why they're using electrical signalling (it's slower than fibre, heavier than fibre, can corrode, and can short) and whether the FADEC fail-safes are all that safe or just plain stupid. For a start, they get paid to shout at each other, and they actually know what specifics to shout at each other about.
But, if the claims are remotely accurate, then there were a number of well-known flaws in the design and I'm sure Boeing will just love to answer questions on why these weren't addressed. The problem being, of course, is that none of us know which of said claims are indeed remotely accurate, and that makes it easy for air crash investigators to go easy on manufacturers.