Move tool leaves clicked part of selection behind?

Hi! Very new user fiddling with the trial of storyboard pro. The tool had been working as expected for majority of the free trial, but now when I encircle my selection, use move tool+shift for a straight line, and click on one of the lines to drag my selection where I want - the tool will leave that particular vector line behind, deselect it, while moving the rest of it.

This leads to: if I click another part of the remaining selection so I can keep moving it, then one by one, all the vectors are deselected, and dragged-n-dropped all over each other. As I said, it was working fine for majority of the trial, and now I don’t know if I can finish my work with this snag ruining any frame I need to adjust.

Have I just turned on a setting somewhere I didn’t realize? Video of my issue: Move tool leaves clicked part of selection behind? - YouTube

When you say “move tool” are you talking about the ‘Select Tool’ (Black Arrow/Pointer). When using the Select Tool with shift this allows for selecting multiple objects/stork or deselecting them. This is what is happening, you are deselecting the object/stork and then invoking the constrain angle. So when doing this it is best to be close to the centre pivot point (Pointer will change to the Four Arrows) and then move. Or you can do your selection, start moving it and then hold down shift to constrain.