If trying to fix this problem, you may first restore, flash, or update the device flash firmware. If the restoring or flashing doesn't fix the signal problem. You may then proceed to hardware troubleshooting for check up procedures on some certain components on the PCB board. refer to the solution below for it shows the RF circuit of the 6730 classic.
If all the supply voltages is okay, you may start reworking or replacing the PA IC's then to the RF transceiver and the last part will be the VCTXO.