there seems to be a bug when defining a shallow 3 point plane. Only if the slope is high enough the plane is created properly.
Its not just a matter of vizualization, lines or arcs which are drawn in a cutting plane view on that plane are wrong as well, don't inherit the targeted slope.
Also, on reopening the plane manager the 3 coordinate fields which define my plane are empty.
Can somebody confirm this. I'm using the latest 5.10.7117.27571