electrical short 1 channel. Cable spade at fault?

Make sure it's the amp and not the cable. Either switch cables left and right or try another set of cables (even lamp cord) just to be sure.

If it's still the amp, check for any fuses that might have blown if you did short it out.

Always try the free stuff first before you have a repairman try to fix it.

No guess as to what it might cost if it's a worst case scenario. Good luck.

Good advice from Onemug, if it's the amp your best hope is that there is a fuse in the circuit that protected the amp.

I had an Audio Refinement Complete integrated, the predecessor of the YBA 201, I think, and blew out the right channel when a pair of speakers arrived with an internal short. There was no fuse in the circuit and the cost to replace all the blown resistors was just about exactly the value of the amp, ~$500. I paid it rather than throw the amp away but it wasn't fun.

Yes, I tried all the permutations including another amp and it is the YBA R channel.
Sfar,that is exactly what I feared about repair cost vs price paid.

Can I hold the cable seller liable for the tab?

No, you can't.