The Auto-Activate Paint tool must be checked in the Preferences window. This causes the materials window to pop up when the paint bucket tool is selected. This also causes that bug. If it is already checked off, then the program must’ve originally been designed for windows (which is really annoying, since windows crappy, it’s not open source, it’s poorly developed, cheap, and it has many flaws in it, and everything is created for it.) I’ve never had a system crash in all of my years in using Mac, but I do hear that windows users experience those regularly. That’s just my opinion on it. Anyway, I would love to see SU Make 2019 at some point, because as all of these replies suggest, it doesn’t work extremely well.