Disconnected Cable Found Message

I found this testimony on the web Disconnected cable found. Please confirm a connection line." displayed for about 30sec each time the unit is powered on, then the message disappears and all work fine.
Since it is still under guarantee, I contacted Kenwood support many times...
They first kept replying to check my car wiring.
The wiring is OK and was the same from the beginning.
The unit worked without this message for few months, then it has appeared.
Finally, Kenwood Support France admitted that there is an internal defect and accepted I return the unit under guarantee.
I waiting for it to be back.

Please perform this

would check the amp unit for moisture damage, as a marine items is a specially built units that fends off water as well as moisture damage exposture. it does not mater if the amp is enclosed inside the hual or cabinet. The problem you are encountering is most likely because of a bad main amp unit, as if you disconnect the speakers and turn uo the unit, and it still goes into protection or shutdown mode, something is wrong with the amp. Like I said before, the fault is most likely due to water damage or moisture damage to the main printed circuit board.

Thanks

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Troublshooter101