Steps to reproduce:

• Open the template dialog and select a template or wikitext part:

• Click in a parameter's checkbox to unselect it:

What happens:

• The parameter select list is focused and keyboard navigation begins. This is strange because it's the only case in which this happens: clicking the checkbox or label to add a parameter do not focus the select list.
• If the previous selection was outside of the parameter list, then the first element of the list is highlighted and cursor keys will move the selection starting from there. This causes wacky scrolling if the first parameter wasn't already visible (more about that in a new task).