It's been a few weeks since I disconnected my shore power and look what I found!

That is the ship systems outlet.  Until I took it apart last night, it was working??
We have only blown the shore breaker twice in the last three years.   We did use a Y cord to share the ship and AC feeds from a single 30 amp circuit and the AC outlet is just fine.  My guess is that I had some corrosion on the 30 amp connector causing a high resistance connection.  The ship master breaker and sub system breakers never tripped.
Before leaving the boat last night, I swapped the AC outlet to the ship systems outlet.  All is fine.  
I do plan on using separate cables from now on.  I am replacing the outlet and the cooked cabling inside the boat splice box this weekend.
Any other ideas?
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Jnizi
2007 Vista 338 "Better Yet"
Previously: 
2007 Vista 258 " Just Right"
2005 Horizon 230