In InDesign 16.0.1 x64 in the Drop Shadow section of the Effects Dialog Box, there are some values where the arrows are not working. They are 1) Distance, 2) X Offset, 3) Y Offset and 4) Size (marked on the attached file).
These values should change(increase/decrease) either by pressing the arrows on the keyboard or the little arrows to the left of the value. This isn't happening in the latest version of InDesign. I looked at other effects sectios and the arrows seem to work everywhere else.