EndNote 9.3.1 Bug: reproducible crash & work-around

On macOS Catalina 10.15.1 (and earlier) , Macbook Pro late 2013, EndNote X9.3.1 and X9.3:

If an old (X9.2) library file is selected to be opened (also when double-clicked in the Finder) while there is already an open library in the program, EndNote crashes while attempting to upgrade the version X9.2 library.

The X9.2 library can nevertheless be updated if no other libraries are open in EndNote X9.3