Pioneer pitch/tempo fader fluctuating massively when not moved + inaccurate

Hi there

I have just bought a second hand 850 of gumtree after using a controller. I came home and tried it out, and the pitch fader first off is stiff/gritty feeling just below the 0 mark. More worring is that the tempo seems to flutuate huge amounts without me touching it, and when i try to adjust itit seems completey off and also fluctates away form what it should be.

It's not just the bpm counter, which, after doing my research it can be inaccurate if you are you are using non rekordbox anazlysed mp3s (please not that i just copied over an mp3 file onto a usb just to try it out without downloading rekordbox etc, and I won't easily be able to try this option as I am away and thought if i need to send for repairs it'd be best to leave it at home where other could take it, but I could ask them to try it for me!). But it's also the (+/-) counter which is fluctuating madly, where i set it to what should be (-) close to 0 and it's deviating madly between say (+1.00) to (+2.50) or something similar, the biggest change i noted was (+/-) about 1.50.

It also seems to work fine and be very responsive at the largest (+) mark and pretty good but not amazing at the furthest (-) mark, especially when you put a little pressure downwards.

I'm praying that this is just me being a retard, but fear as its not just the bpm counter but also the (+/-) counter alongside, and that its also such large fluctuations that it's faulty. Lastly I'm pretty sure that it wasnt just the counter that was fluctuating but also the tracks tempo as when it decided to stay it sounded more stable/different to when it was changing, although I can't say for sure as I was a bit mad u kno :/

Any help of guidance would be lovely, thanks in advance.