It looks like you’re defining what units you’re using in the experiment settings for most of the components except the sliders, which have their units defined in the component itself. That might be the source of the issue here. You could try either having the sliders use experiment settings for their units, or if that doesn’t work, try manually setting the unit type for each component (tedious, I know, but the easiest way to narrow down the issues).
My thinking is that “size” is a back-end property that PsychoJS uses to convert from whatever units you are using to the actual pixels it needs to display, which is why you can’t set it manually. If it’s not reading the unit types correctly, then that computation could fail in this way.