After assembling output power stage, things went wrong. Somehow, I managed to burn high power transistor Q16 (2SA1302). After plugging in the circuit to +/-30V, my bench power supply indicated shorted and I knew immediately that something's wrong. After turning the power off, I measured 0Ohm between pins of the Q16. It was dead. For some reason all other transistors were well and alive.
I stared at the symbol, schematic and layout for one hour. I could't see any obvious error. Could it be that I just received bad chips from ebay?
As a comfort, here's a nice photo of the fully assembled board: