Here, I got it. On my laptop the weird slider behavior happens even on windowed mode. Not sure if it's of any help, but I've noticed moving the slider to the right decreases the value (instead of reducing it as would be expected), when I push relatively fast in that direction - since the slider seems to be fighting back and moving it back to the other direction.
https://media.discordapp.net/attachments/288994979748249600/603667584218431651/2019-07-24_16-16-07.gif?width=400&height=204
https://media.discordapp.net/attachments/288994979748249600/603667584218431651/2019-07-24_16-16-07.gif?width=400&height=204