Sometimes my RDS-TMC connects with my tomtom go 930 and sometimes not in a random way. Any suggestions?

This sounds like the connector on the TT or the plug on the RDS cable is at fault. If you continually plug and unplug the RDS and do not have the entry angle exactly perpendicular every time this can damage the socket ion the TT and effectively make it loose. I had this happen with a TT TrafficMaster and ended up replacing the on board RDS socket and then no more problems. Alternatively the right angled RDS plug may have a problem ith the cable at the point where it joins the plug. If you move the cable (not the plug - hold this steady with one hand) gently when it is connected to the TT you may see that the connection gets broken. If so then you can replace the plug on the RDS cable for a higher quality metal one. If you have room use a gold plated straight entry plug with cable strain relief rather than a plastic plug without strain relief. If the unit is out of warranty and you are capable of using a fine point soldering iron then you can replace the onboard socket for a higher quality gold plated socket.