With Owl Carousel ‘Mouse Drag’ enabled the JavaScript ‘Mouse Drag’ (onDrag) event on the slider is assigned to scrolling the slides forward and backwards (slide navigation). This overrides the ‘Drag-to-Scroll’ (up/down). It seems you can ONLY have the ‘ondrag’ JS event mapped to a single function here – scrolling slide navigation, OR scrolling slide up/down.
Also remember that I build my plugin using the JavaScript plugin ‘Owl Carousel’ (https://owlcarousel2.github.io/OwlCarousel2/). So the actual carousel low-level functionality is handled entirely by this product. Slide Anything is a tool that allows you to add content and generate sliders using the Owl Carousel plugin. So if there are bugs within Owl Carousel I cannot help here. All I can do is ensure that I’m always using the latest release of Owl Carousel (currently version 2.3.3), so any bug fixes they implement are brought across into Slide Anything.