2001 Launch Guages

I have an early 2001 Launch with Faria electronic guages (white Supra faces). The tachometer and speedo's have been intermittent since the first summer, with the tach sometimes registering 2X RPM's and the speedos sometimes registering high or not at all. A light tap on the glass faceplates brought them to correct readings. The speedos have now stopped working except for intermittent registering of one.

The dealer has replaced the speedometer instruments and checked or replaced the grounding, and the two printed circuit connector boards behind the dash switches (nav, courtesy, interior and bilge) and the circuit breaker panel behind dash. Voltmeter was also replaced, but replacement is frozen at 14V and non-functional. Have requested dealer to supply new working replacement voltmeter. Tach now reads correctly, but speedos are not functioning.

One of the electronic cables from the transom speedo paddle wheels had been spliced as boat received from factory. Other cable appears intact.

Can the sensor cables and/or transom paddle wheel sensors be replaced and is this likely to correct speedo problem?

Any help as this has been an increasingly frustrating experience with an otherwise finely built boat (my second Supra).