This problem started with some update to Excel that happened between the summer and fall of 2016. There was a major update to Excel 2016 in mid January that seemed to fix whatever was causing Excel to crash (at least in my testing), but I still think Excel for Mac 2011 is the best version, and all my tools run flawlessly with it.
I am providing people who have bought my tools and are still experiencing this crashing problem with the latest version of Office 2016 (an installer for Office 2011 that they can use with their license of Office 365. Again, this seems to only be the case for macOS, and is just an easy fix until I can get a better solution in place.
Thanks for understanding,
Richard Boutwell