Spectron Musician ii issue

I bought a Spectron Musician ii Hybrid mk ii (serial# 2065) off Craigslist a couple years ago. I loved the amp and got a few great years out of it. 

Then I started having problems with the right channel going silent. I took it to their service technician. I live in Los Angeles so it was not too far of a drive. He fixed it once, it went out again, and he fixed it again. I was in the habit, by this time, of leaving the amp on all the time. One day in October I came home and smelled smoke coming from the living room. The smoke was one of my Magnepans which was in the process of melting. As I rushed to unplug everything I could feel that the Spectron was extremely hot. I disconnected all the components and took the system apart. The speaker was ruined and had to be sent back to Magnepan.

In my final configuration, I was using the remote sense speaker connection and the balanced (XLR) inputs on the Spectron. This is how it was connected the day the speaker melted.

From everyone I've talked to, the theory is that the amp had somehow gone DC on the right channel and turned the speaker into a heating element. 

I took the Amp back to the Spectron technician who could not find any problem with it. He recommended having the preamp checked. The preamp is a brand new NAD M12. I took that to Henry Radio in Brentwood and it came back with a clean bill of health. 

I then took the Spectron to Shelley's Stereo in Woodland Hills to see if I could get a second opinion. (That's where I bought the Magnepans and they've always been super nice.) They took the Spectron in and sent it to a third party who reported back to them that the amp was unfixable. At this point I don't know if they mean it's unfixable because it's full of proprietary components or if they have identified a specific problem that is unfixable. I've been trying for a month to get a written evaluation from the vendor that Shelley's uses for service but so far I can't get a response.

I accept the fact that buying off Craigslist is a risk, and in this case I have no warranty rights. In fact I'm not disappointed with the experience. I got a few years of great listening off this amp and it was a huge step up for me at the time - definitely introduced me to the joys of a higher class of amplifier. I'm just wondering if I'm at the end of the road with this unit and if I should give it up for dead. Because of shipping and repairing the speaker, plus the second opinion on the amp, it's already cost me $600, plus 3 months of no music in the house. I'm a patient and methodical person by nature, so I enjoy problem solving, even this kind of problem. But I'm not sure how much more money and time I want to spend on this problem.

Any advice?
Agree w all above.  If you are looking for an amp that is reported to play nice w Magnapans, with an impeccable record of after sale service (even to secondary market buyers) consider Atma-sphere. 
I run a pair of these in mono config, also with remote sense cables and leave amps on all the time, have done so for years without problems. I have had a couple of repairs/upgrades over the years, sent both amps direct to Spectron -- is that where you went when you said a Spectron technician examined it? I would think if your system had the meltdown of a speaker, then I’d really worry about using this combination again but I’d want Spectron to look at the amp and confirm what the problem might be. It’s possible the problems lies elsewhere in your rig perhaps (which is what this ‘technician’ seems to be suggesting). Did Magnepan suggest what the problem might be?
Your story sounds a lot like mine. I dumped my third Spectron a few months ago in favor of a Rowland Continuum S2 to drive my Magnepan 3.7s.

This amp has been referred to in another thread as "Kryptobrand."

I started with a Musician II, used.  It experienced issues over time, some of which included sparks and smoke.  The right channel -- for whatever reasons -- has always been an issue in my amp and those of some others.  Eventually, they convinced me to upgrade to the Hybrid.  I got a year or two out of that before failures occurred, and it spent much time going to and from California.

They could never seem to articulate what the problems were...

Eventually I got weary of that, so upgraded to the MKIII se2 with all the bells and whistles. That worked for about two years before the right channel dropped out.  After much diagnostic time and swapping of amp modules -- complicated by the fact that the problems were intermittent -- I sent it in, got it repaired, and decided I had had enough. Time to sell.

Also aiding my decision to sell is that all of the principles at Spectron passed away in the last year or two.  John and Toni Ulrick are gone. Simon is gone.  This leaves Manh the engineer holding the bag. Fortunately, I sold my relatively new Spectron to someone who is technical enough to deal with any issues that might come up, as he has worked closely with Spectron in the past.  It found a good home.

I spent weeks testing various amps before settling on the Rowland integrated. It sounds great with the 3.7s.  Also tried Bel Canto REF600M, Merrill Veritas, Sanders, and others.

My advice echoes others': Move along, and enjoy the process of finding your next amp.

A month ago one of my mono Spectron amps had no sound.  I sent it to Spectron and they had it repaired and returned to me within a week.  And since it was still under the 7 year warranty, no cost to me. Excellent service!
Just to add to what @bostonbean was saying: I always found Spectron's service to be attentive, cordial, and effective. I never had any complaints about dealing with the folks at Spectron.

I did, however, get tired of amps failing and having the house go quiet for weeks while the amp was repaired and in transit.