Editor window size bug?

Hi, I started to notice that for some reason my design in PG was a lot smaller than when I previewed/exported.

So after lots of playing around to find out what was going off I found a strange bug whereby if I drag the right side of the window BEYOND the right panel (that shows all the DOM parts) and the let go, it springs back to where it was but the viewport gets smaller.

The only way to get it back to normal size is to drag the window all the way to the left size until its completely gone, it then srpings back a bit but the viewport is back to normal size?