Empty space, where the slider should be (phone, tablet)
Slider doesn't show up on phones, there is only an empty space, where it should be.
Other possible solution
Also this problem can happen if you are using JotCache, which puts <jot... > tags around the module positions, so if you use it, you can try to turn it off in the Extensions → Plugin Manager → JotCache and JotMarker, to see if that helps.
If you are a more advanced developer, this documentation could help more.