@VectorStyler Thanks - I think the issue for me is that the collider tool is set to the forefront in that tool grouping by default and even if it's not being used, if it's icon is visible in the vertical tool bar, it affects the way the transform tool can be used. I was getting the collider symbol to appear by my cursor even when all I was doing was trying to shift-click several overlapping vectors - this caused them to not select properly. I was not trying to use the collider tool, at all in this case and it still was in part activated.
This is a similar issue with the magic wand tool - if it's the visible top toolbar icon in it's set on the vertical toolbar, other selections cannot be made until it is switched away from entirely.