JQuery UI range slider handle moves out of control when sliding

Whenever I click and try to move a JQuery range slider ui handle, the handle moves leftwards to have the exact same value 94. I could not simulate the problem in jsfiddle, so I am linking a video to display the issue : Youtube Link I suspect that the problem has to do with _slide function because the handle does not move when I just click it. The problem did not happen when I was not using a shadow dom.