This maybe a clue to what you see:
Move means to move an object without regard to other objects that connect to it.
Drag means to move an object and have any connected objects remain connected to it.
My bet would be you were moving instead of dragging.
Not sure if this is a bug or intended behaviour. If it is intended behaviour, then I have no idea why it was designed this way...
My problem is that when I am dragging a pre-existing track on a PCB layout that has only two vertices, interactive routing rules are not obeyed. This means that you can drag the track anywhere, including on top of other tracks. If you reshape the existing line segment first (add more vertices), then subsequent dragging will obey interactive routing rules.
I'm running Circuitstudio Version 1.5.2 (Build 30)
Here is a video demonstrating the bug: