Hafler 220, one channel out of sync HELP

Tubes you can rebias.
Transisors are biased only once by the manufacturer.
I'd suggest replacing an output devices along with bypass electrolytic capacitors.

Hafler Mosfets and cleaning. I saw a tweak on the internet about cleaning the the Mosfet pins and pin sockets. It must be done carefully but I must admit the difference was stunning. As they are not soldered in (anyway in my Hafler 200 they weren't), the pins and pin sockets get cruddy after 20 years. Again, caution is recommended in removing and cleaning. Still and all, the improvement in sound was well worth the effort and it costs only time. Good Luck. p.s. Get a copy of the Jung/Marsh POOGE article if you really want to dig into the Hafler.

Solderless output???
I'd use solder in that case.

I STRONGLY URGE YOU TO REPLACE THE CAPS. I have recapped several old pieces within the last two months. One of which was a Hafler DH-500. This amplifier sounded horrible; and basically couldn't be used. After the recapping, it was much nicer and is being used by a friend of mine. The caps were 20,000uf 100v, so they were sort of expensive (~$100). However, I don't think the caps in your 220 will be nearly the size. I used a site called mouser electronics to order parts. E-mail me with any questions.

re-cap is just a part of maintainance but sometimes it can't fix the main problem.

OK - I realize this was months ago - but anytime a Hafler amp does something strange but still makes distorted sound - check the protective fusses - these are usually easily accesible from the rear panel of the amp.
If memory ( a always fallible thing at my age) serves - these fuses where placed in the feedback loop - the idea was pretty good in that you didn't have a fuse in series with the speakers ( think about how strange the idea of hooking up garden hose diameter wire between amp and speakers is - if ALL this power is going thru a hair thin fuse filament wire?) Hafler got around this - but it does mean you will get distorted sound out of a Hafler amp when the protective fuse is blown.
Finally - check the B+ and B- rail fuses - in audio hell use (bars) - I've had customers blow rail fuses and still not suceed in blowing up DH series amps. and yes - beat on 'em enough and you can break 'em.