DDJ SR Issues - Crazy Buttons

Hi, I know from looking at the forum that this is pretty old ground, but I'm struggling to find much info on whether anyone got a successful fix, what the solution actually was and how much it cost?

Below is my problem, in quite a lot of detail (and what I have sent to Pioneer support) - is this what other people have been experiencing?

I've got a DDJ SR and some of the buttons have started acting bizarrely, making it very difficult to use.

It's all on the left deck and this is what I'm noticing:
FX Assign 2: makes loads of light flash and the software view on the PC screen change each time I push it
SLICER: makes lots of lights change, loads up the same track on right hand deck and plays ie. seems like it's Instant Doubles
FX Select On: the first 2 buttons work fine, the third button turns ALL FX on (left and right deck)
Pad Plus: Doesn't work

As well as the above, none of these buttons actually perform the function they should when pressed.

I've tried multiple USB cables. I've tried both Serato DJ and Recordbox - same behaviour in both.

Interestingly, when I go to MIDI mapping in Recordbox each time I press one of the above broken buttons I get a different MIDI signal - it looks like something is seriously awry with some connections or mapping!

This isn't a very old unit - its manufacture date is Aug 2015, less than 18 months ago and it's been looked after well.