Hi8 shows 'DEW'

Removing it will force the dew circuits to be permanently triggered.
With what did you 'shunt' it with?   A dead short is generally quite safe,
but I prefer to use a low value resistor (less than 100ohm and occasionally
less than 10ohm.)

This is a definite case of 'or what' - because these sensors really do
operate the opposite to what you'd expect, ie, they really do go high
resistance when moist and low when dry.

If the short/shunt DOESN'T prove that the sensor is at fault (ie, if it
doesn't get it operational again) then the problem is possibly caused by a
bad solder joint or faulty plug/socket that attaches the sensor to the main
PCB.  This is far less common than a faulty sensor though, and the other
possibilities are so remote that they needn't be considered at this stage.

Cheers
Rod

The sensor itself is probably at fault (Quite a common problem). It is best
to replace it, but you can easily prove that it is faulty simply by shorting
out its two terminals (these sensors go high resistance when moist or
faulty, low resistance when dry and OK).

Cheers
Rod