Shift "being held down"

I come across this problem when trying to Orbit, it Pans instead. I found out that it goes into the add/subtract mode when selecting. I think Shift is being held down. I actually hadn’t used the shift key in the previous 5 mins. I checked my computer and nothing is physically on the shift key. Pressing it fixes the problem. The key itself doesn’t seem to be stuck.
Is this my computer’s fault or SketchUp Web’s?

My guess is that Shift was pressed in SketchUp and focus was switched to some other tab/window before the Shift key was released.

I tried doing that intentionally and nothing happened.