Well for now partial refund it is! They gave me back $337 + tax (11% here) so now instead of about $640, I paid $246.
For $246 I'll date the dime any time and see how crazy she is in the long run. It's from eBay Fastcrap whom I've bought from many times; they are awesome and have a hilarious name. It was advertised as fully functional and they immediately offered to take it back, but I asked about a partial refund, they offered $250. I sent a note and a counteroffer of $337 back, they said OK. I'll install the switch tonight in a working environment and make sure she's not completely dysfunctional. With eBay I can still get a full refund for 30 days if she's totally crazy.
I am still hoping to fix this switch.
I don't have a thermal camera now and that would help, [EDIT: pulled camera out of packing for move to new house], but I am quite good at tracking down problems. It could be a problem with an important chip, but there is a very high chance it's just a shorted cap or fried resistor someplace. After I run it for a week and have some free time (like that ever happens) I'll try and find what's fried again.
Thanks to you all for your technical help, opinions, and encouragement.
Kind regards to
fohdeesha and all of you who have been there for me. I truly appreciate all of your assistance!