This was brought to my attention by somebody else but I had the very same problem and I'm hoping somebody here notices and can relay this to tech support or whoever is in charge of this.
Here's how to easily replicate this:
Set your DPI to something low like 200.
Open Paint and hold your left mouse button and then do very quick up and down movements.
The mouse should shoot left or right if you do it fast enough (I couldn't upload a file for some reason so here's the image
https://goput.it/xvhh.png)
It seems the vertical malfunction speed is far lower than the horizontal. This problem is also FAR worse and easier to replicate at 2000hz.
I hope this is something that can be fixed with a firmware update.