I’ve faced strange behavior while moving objects within mockup with mouse. Instead of moving an object while dragging, I see a list of mockups are moves.
When the object is placed in a left half of the screen, the mockups list is moving. When the object is on the right half of the screen, the contents of the inspector panel is moving.
Please watch the GIF:
The bug appears after some time of working. Page reloading fixes it for a some time.