As other stated, the problem is likely corrosion or a loose contact.
However, earlier versions of the Raymarine course computers
(T100 & T300) had a problem if the SeaTalk
network power lead was connected both to the course computer SeaTalk power lead and an independent 12V power source. In this case if the power source for the computer is turned off and the SeaTalk network is still powered the computer will attempt to pull power from the SeaTalk network. Because of the thin power lead in the SeaTalk cable this could result in a low voltage condition on the SeaTalk network.
I don't know if this issue still exists in the current
, but if you find nothing with checking the electrical
connections, then double check that the SeaTalk network can get power only from the computer and not from some other source.
Back with those earlier computers Raymarine recommended that the SeaTalk network not get power from the computer and that the SeaTalk power lead (Red wire) not be connected to the course computer.