I've had many crashes by dragging materials from the Content Browser directly to objects or replacing an existing material in the Material Manager. In this crash, I had the IR running, but I have had this crash without any rendering going on.
It took 10-15 tries to get the crash. It's pretty random, but maybe there's something you can find in the report. Uploaded file is: "Crash_DraggingMaterialsToManager.zip"
Full-speed non-debug version
Build timestamp: Jul 2 2021 15:04:17
Version: 7.0 rc 2
Cinema version: R20.059 CINEMA 4D Studio
MacOS Catalina 10.15.7