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Replacing the 100 ohms at the six emitter resistors of the bidi amps with 220 would explain the higher collector voltage at Q2, Q3. ?No reason for Q1 to be different than Q2,Q3 on receive, signal levels are down in the microvolts and the quiescient voltages and currents are well isolated by caps C11 and C13. ?So I'd zero in on Q1, there's only about a half dozen parts that might be at fault. ?Primary suspect is your new 220 ohms at R12, is it really 220 ohms? ?Is it really soldered down properly with no cold solder joints? ?With power off, compare ohmmeter readings across R12 and R22, but avoid direct contact with R12 because those solder joints are suspect (so maybe put the probes on the R12 side of C12 and the ground end of R11). ? How do the DC voltages at the base and emitter of Q1 compare with those at Q2? ?Q4 likely has the same problem as Q1, whatever that is.?

Trouble at Q1 and Q4 could explain low audio volume and no transmit power. ?And possibly even why the audio fades out, though that seems more likely to be at C113. ?I'd simply remove C113 entirely till all this gets sorted out. ?Without C113 the audio out will be somewhat reduced, but still good enough to hear. ?If audio still fades out after a few minutes, maybe watch the voltage at C110, see if that drops with your audio volume. ?Maybe wire up some other audio amplifier or some high impedance headhones to M1, see if audio is good there.