DDJ-400 left tempo slider completely unresponsive and causing issues within rekordbox

So a few months ago my tempo slider on the left deck decided to stop working. No matter how much I move it, it's completely unresponsive and doesn't change anything in rekordbox. As my 1 year warranty expired literally a few days before this happened I've had to make do and use beat sync to make it work. If I want to change the tempo mid-song I have to mirror it onto the right deck and use the tempo slider as the one on the right deck is fully functional. A bit frustrating but not the end of the world.

Anyway, where I really ran into trouble is (only on the left deck, I presume has something to do with broken tempo slider) say I'm playing a track at 126bpm sped up 3.2% (song originally 122bpm), it will randomly throw itself back to whatever the original bpm is.

I have no idea why this is happening or what is triggering it, and it is happening extremely frequently now which makes it essentially impossible to mix on my decks now.

Here is an example of it happening (happens twice in this video): https://streamable.com/qqj6ml