Baffled - VBA works in Excel 2010, but Excel sometimes stops working with 2016

[mwc0914]

I have a macro I wrote in Excel 2010. We have upgraded to Excel 2016. Now the same macro sometimes works, other times, I get the message that Excel has stopped working.
I am running Windows 7 64 bit. Excel (both 2010 and 2016 are 32 bit). The macro sits on a network drive and is executed from there.

Any ideas what could cause Excel to stop working...."at random"?