I've had my '17 Turbo since early October. Sometimes I get a warning signal that the seat belt is not connected (it is) and that the adaptive cruise control needs servicing.
Wondered if these two items were on the same circuit - thus blown fuse. But no, on start-up after overnight no warning signals whatsoever. Concluded that the circuit(s) fuses are operative.
Former owner of this car lived in Newport Beach, CA - in the "salt air zone." Salt air can cause corrosion of chassis ground points. I cleaned the battery posts, but this problem continues. I'd like to clean any the chassis ground connection, which I think exists. If so, where is it?

 

usually, there's a fat ground at the engine block - that's one of the main ones.

 

Hopefully the seatbelt warning issue is local to the belt and latch areas. Is the warning the seatbelt unbuckled?

 

The seatbelt warning came on when the seatbelt was fastened. I unfastened the seat belt and refastened - still the warning. Problem ceased after an overnight cool down as mentioned above.
On ground straps: I've seen high-end audio shops install additional grounds to head units and amplifiers