NOTE: This issue was fixed in the latest ARCHICAD 20 Update 4012 and ARCHICAD 19 Update 7006.
The GRAPHISOFT installed Quicklook Satellite and Spotlight Plugins can crash when opening ARCHICAD projects. These two Plugins help display additional information about Projects in the Apple Finder (preview picture, file version, platform where the file was created, other metadata, etc.).
The crashing of these plugins can cause general performance issues because the apple crash report system runs in the background quite frequently.
The security policies for Plugins like the Quicklook and Spotlight became more strict on macOS 10.12 Sierra therefore the crashes are happening more frequently.