The AC21 tool does not crash, however it takes a long time (~10secs) for a single, very simple object.
Not sure if its related but I've recently upgraded to macOS 10.13.3
this is the first time i can recall ever having the tool crash ..
Just double-checked 10.13.3 with AC20 and AC21 converters and both seem to be working normally. Perhaps there's a problem specific to that object? Is it causing problems with other objects that have previously worked correctly?
Ralph Wessel BArch