PPAv2 output buffer problem

I'm building a PPAv2 amp, and have most of the parts soldered in following Tangent's guide.  I made it to the stage where the buffer bias is being set.  Channels left and right were easily configured to 20mA (measured 44mV); however, the ground channel had a problem where for some range of the trim pot it would be extremely low, around 6-8mV, and then after some threshold, it would jump to about 60-70mV.  In both ranges, adjusting the pot further would affect the mV range, so I don't believe the pot itself is defective.

Other information:  I figured that 30mA for the bias would probably be okay, so I set all the buffers to 30mA (~66mV measured across the 2.2ohm resistors).  I proceeded to solder up the rest of the board and nothing heats up or is smoking.  In later tests, however, the output voltage bias is extremely high for the ground output (like half a volt), which means something is terribly wrong.  All op-amps are receiving the same stable voltage, and nothing else seems to be affected.  Both 2.2 ohm resistors on the ground channel show the same voltage when measured

How should I proceed to troubleshoot this?  I've already replaced Q4, to no avail. I'd like to avoid replacing all the transistors in the buffer, though I do have spares for all but Q24 and Q34 if I must.

Thank you for your help!

Thanks for the reply.  I did try to do my homework before asking for help, and went through the troubleshooting article as well as the PPAv2 construction forum but haven't been able to find any solutions there (though it is quite large).  I will, however, move any future questions to that thread.

For your suggestion, I replaced R11 with a 100ohm resistor but now the current ranges stay only in the low single digits, and the offset remains. I'll do some more tests and then ask in the other thread.

Thanks again!