Adam,
I believe the bias is set by R17 & R18 show in the detail from the schematic below:
T2 is the trifilar wound inductor. I think one interesting test would be to see what happens to the voltage at the R17/R18 junction when the problem is there and when it's not. If it is then my guess is something up stream is getting shorted to ground. Maybe reflowing T2's connections?
I think you might want to consider the if T/R switch Q6 is working properly.
I'm familiar with Rev 3, 3a and 4 boards. If you have an earlier version some of this might not apply.
Good luck with your troubleshooting!
--Al
WD4AH
