Ok. @Djon first of all. You have to give a lot more information. This is from a project you posted in another post (that was for another problem) but the slider you are referring to is running a function on mouse click to update the amount in the text element. You should use on Mouse Down (Touch Start) if you want it to run in iOS
Second;y, I would refain from using playbackRate in iOS as it can have funny affects.