Same problem here.
And here
http://archicad-talk.graphisoft.com/viewtopic.php?t=55095&sid=608831c5252e72a84ed97059ae6c2e82.
And here
http://archicad-talk.graphisoft.com/viewtopic.php?p=267422#267422.
Seems an issue with Macbooks, Sierra, and AC20. We're on Build 5025.
Chuck Kottka
Orcutt Winslow
Phoenix, Arizona, USA
ArchiCAD 25 (since 4.5)
Macbook Pro 15" Touchbar OSX 10.15 Core i7 2.9GHz/16GB RAM/Radeon Pro560 4GB