Parking sensors not working correctly

[Jake06octy]

Hi everyone i have a skoda octavia elegance 06 1.9 tdi 

The rear parking sensors are not working correctly i have listened for the clicking of the sensors which are all active but one is slightly more faint than the rest i have about a second of the picture come up on the screen whilst shifting from reverse to first and both my reversing lights are working any ideas to how to fix this? Could it be the slightly quieter sensor? Also my back window wiper and jet has stopped working 

[pikpilot]

There could be common source for all your problems which should be checked first.

Take a look in the boot on the passenger side. You may need to remove some trim dependant on your model variant, but find where a number of brown wires are connected to a metal stud(s) welded to the body side or floor.

This is the earth/negative connection for the rear functions.

Water in the boot or released when the rear washer supply pipe has frozen and come off/split (washer fluid low  concentration) can cause corrosion of the stud/ring connectors/ wires.

 

This should be checked first before exploring the many other possibilities,

[raf300]

Good reply above. I had similar problems where y my rear parking sensor only work when the weather is very hot. 
Which could suggest a connection issue is not strong enough