I couldn’t manage to replicate the issue you had with unselecting, did you play with a mouse or on a touchscreen? To unselect an object you have to right click somewhere else, or do a long press on touchscreen. Let me know if it does the trick ;)
Browser & mouse. I went back, and I think it was my confusion. It was hard to tell the difference between hovering over a square, having something selected and right clicking to deselect, and using the ✔ and ❌ to “deselect” as well. They seem similar but not if that makes sense.