Pioneer DJM 800 VU meter problem

I have a problem with my DJM800. When I put fader 2 up, the VU meter of channel 2 lights up wich is what it's suposed to do, but the VU meter on channel 1 shows the same signal as on channel 2. This also happens when fader 3 is up, channel 3 and 4 show the signal of channel 3. 
Note that no sound is leaking from a nearby channel, it's only the VU meter.
Does anybody know how to solve this?

Thanks in advance.