You should be able to get things working again with out sending it in. I suggest cleaning the b-button switches using Caig's DeoxIT D-series contact cleaner -->> store.caig.com. Using the included straw applicator, spray a good amount of cleaner between the b-button cap and top cover, trying to get as much as possible into the switches. After applying the cleaner, press the buttons several times to work the cleaner into the switches. The DoexIT will clean the contacts within the switches and should resolve the problem.

Thanks a lot.

No problem! :)

Is it important that the mixer be powered OFF while applying the contact cleaner?

Not necessarily, but I would, just in case :)

wondering if you have heard of mods for applying deoxit with out having to remove the cover/botton caps?
like a straw out the vent perminly attached to the contact
or a hole in the button cap that could be sprayed down?

Spraying DeoxIT between the top cover and "B button" caps typically allows enough contact cleaner to get into the switch with out needing to remove or disassemble anything.