If you are using Office for the Mac 2016 and you have the 15.20 release installed, Microsoft introduced a bug that causes all add-ins to crash Word when you quit Word without opening or editing a document. The same thing will happen with Excel.
This is a Microsoft Office problem and not the add-in’s problem. Microsoft is aware of it and hopefully it will be fixed in the April (15.21) update. Many people (users and developers) are screaming about it on the www.answers.microsoft forum.
If you want to remove the Got-Ur-Back GUB add-in go to these paths on your computer and move the GOT-UR_BACK add-in you find there to the trash.
<Your HD Name>/Library/Application Support/Microsoft/Office365/User Content/Startup/Excel
<Your HD Name>/Library/Application Support/Microsoft/Office365/User Content/Startup/Word
We are sorry of the inconvenience this has caused you and we wish there was something we could do about it.
We released the GUB application to Office 2016 for the Mac in December 2015 and all was working flawlessly with our customers until mid-March 2016 when Microsoft pushed down the 15.20 update. The application still works and you will not see crashes in Word if you open and work in documents… the crash only occurs if you open a blank document and then later quit Word without ever working in the main body of a document.