Apple MacBook M1 Pro with External monitor - Select not working properly

Working with RhinoWIP latest V8 I have trouble on my external monitor (Dell 4K 32")

I create a box in normal 4-window mode. Then Click on Perspective to make one large Perspective window. Now I can’t select properly. my sample frame shows me holding down the mouse button in lower right but selection is happening in the bow as shown. Change back to 4 window or work on internal monitor and its OK.

Thanks for your help! Happy New Year!!