[2019] Minor Bug with mouse wheel

Are you holding shift?

Capslock will toggle an overlay which shows stack counts. Holding shift toggles between changing camera layer and camera zoom. Also, there seems to be a bug where holding shift and then switching to another application will lock the toggle. Though, I don't think this is the case for you.

Ok. Do you have a second mouse to test that with? It could very well be a hardware issue. I'll look into it regardless.

It's likely not your mouse, I'm just covering all the bases. Thanks for all your help. :)

There's no in-game method to reset that but -- and I know this is a cliche answer -- have you tried restarting the game? Does it persist after that? Alternatively, try resetting the hotkeys from the settings menu. I doubt this would disable that stuck functionality but it's worth a shot.