I believe I hear you say that you have a good phasing signal at lugs 2,3,4 and 5 of the DPDT switch in the 90 position. You should also have a good “dry” (clean) signal at the lower pad of R18 that connects to pin 6 of IC1. If so, the mixed signal should appear at the Base of Q5 and at R19. If you are losing the signal there, check for a cold solder joint in that area or near Q5. Another possibility may be a short to ground in that area or beyond Q5. Remove power and use your continuity test on a DMM to look for a short to ground.
One final problem I fear may be a faulty Q5. SInce you did not use sockets for the transistors, you may have damaged Q5 with heat. But, let’s look for these other possibilities first.