You need to make sure that you don't miss out any commas when using zscript commands. With your button you have missed out the pop-up info, and with your slider the comma is missing after the pop-up info. For the slider this means that the "1" for the slider width becomes instead the enabled/disabled parameter.
[IButton,"Zplugin:TEST:512","Pop-up info about this button",
[IPress,Tool:UVMap:512]
,,.2]//end button