Selenium IDE inconsistent Mouse Down, Mouse Move At, Mouse Up test

[Zach]

I am attempting to automate a report page and need to grab a horizontal scroll bar and move it over. Here is an example of the commands, targets and values I have recorded. 

mouse down at

css=.dx-state-hover > .dx-scrollable-scroll > .dx-scrollable-scroll-content

391,4.109375

mouse move at

css=.dx-state-hover:nth-child(2)

1,4.109375

mouse up at

css=.dx-state-hover:nth-child(2)

1,4.109375

css=.dx-state-hover > .dx-scrollable-scroll > .dx-scrollable-scroll-content is the scroll bar element that I want to move. 

css=.dx-state-hover:nth-child(2) is the element in which the scroll bar is contained. 

I have seen this work and move the scroll bar in some tests, but in others the scroll bar will be highlighted but not moved. 

I am very new to automation and have little to no programming knowledge. Any advice is appreciated, thank you.