So it turns out that my recapped Sansui AU-417 had distortion in the right channel. I contacted the seller, and he had me try Deoxit (and I also did a DC offset check), but no joy. So, he had me send it back to him (it turns out that he does the recapping & glue cleanup himself as a hobby - his feedback is full of various AU-x17 amps).
He received it and he reports that it was a broken solder joint. When he re-soldered the joint, the distortion went away. He readjusted the DC offset and bias and has shipped it back to me.
So, the morale(s):
* If you are looking to fix an audio problem in vintage electronics, be sure to look for bad or broken solder joints.
* Shipping of old gear is liable to shake something loose.
And it is cool that the guy wanted to stand behind his work...
I'm not sure whether you would have heard this news or not, but Butch (the gent who restored your amp) sadly passed away about a month ago.
Please continue to enjoy your amp, knowing that you're listening to a piece of gear that was lovingly worked on by a true gentleman and vintage audio enthusiast :)
Thanks for the info. I will remember him when I listen to the Sansui. (BTW, I am behind on this thread and hope to catch up after the holidays.)