This is a bug in the current version of Sketch on iPad Pro. It will be fixed in the next update (which should be here very soon). In the meantime, try this: Go to your Device Settings\ Display & Brightness\ and set the Display Zoom\View to “Standard" (the “Zoomed” setting seems to be causing the bug).
Let me know if that resolves it for you.
thank you very much for your QUICK answer!
it works perfectly!!!
what do we learn from this? Don't change your Display View!! Not even for your 78 old dad!!
You're welcome. Like I said, I believe it's fixed in the next release, which is imminent, so you can go back to that setting soon.