A more detailed description of the problem you are having would be helpful.
That said, I’ve read in some other posts here that the RF board in the TIU can work it’s way loose. You’ll have to open the TIU to check that. Make sure you disconnect everything from it and ground yourself to something metal to help dissipate any static electricity. Try to handle the circuit card by the edges and don’t touch any microchips or ICs while the case is off.