Very low output from my right channel

Last night, I played the “channel identification and channel phasing” tracks (#1 thru #2) from the Stereophile's Sampler & Test CD on my EAD T-1000 transport and the right channel was barely audible. For a brief moment I could not figure out how my Wilson Watt 5/Puppy 2 speaker was damaged (VTL ST-150 amp/VTL TL-2.5 pre). After some diagnostics, the real culprit is my older Altis DAP "Reference" Bitstream Decoder. What do you think might have caused me to lose the right channel?

I paid $250 for the DAP and it’s served me very well. It has a separate power supply that is completely separate and has had all of its caps upgraded and is significantly "hot-rodded". There is an updated cord connecting the two items and also installed is a new clock, jitter reduction components and tons of new caps and updated resistors in the DAC itself. It has one coaxial digital input, one AT&T glass input, and one digital coax output and, of course, right and left analog outs.

My options are to fix the DAC or spend $500-$1500 for a replacement. Primarily I listen to jazz and salsa. So folks, what do you think?
I assume you're not a diy-er or you;d have diagnosed the problem yself. So,

If you're happy with the DAC, take it to a technician to check. It could be a very simple matter and cheap to correct.

A new dac would have a more performant chip (yrs is bitstream) in it -- but less fancy componentry. You could buy a contemporary dac (say, a Benchmark or similar) and have it upgraded with your components (many of which are re-usable). Keep in mind that dacs cost 500-1000 and you'll have to add the cost of modding... However, current AD or Texas Instruments chips used in dacs are very good performers -- so chances are the contemporary modded dac will outperform yours.
And jazz deserves good treatment, doesn't it ;)
I'd agree with Greg, get a tech, but I would not sell the DAC, it is a good one and can be further upgraded by Jerry Ozment. The only DIY possibility is a bad tube (I believe the Altis is a tubed unit), you could switch the tubes for each channel and see if the problem switches channels (you'll need to follow the circuit, and make sure you put the 12AU7 and 6922 tubes in the right places). You might also call Jerry Ozment, he's a designer of the DAC and could probably help.