Performance degradation of Native COBOL access to Excel 2016

We have a Native COBOL program that reads excel files using COM Automation. After upgrading Microsoft Office from 2010 to 2016, the program takes about twice as long.

Processing the same 270 files before the upgrade took on average 3-4 seconds per file. After the upgrade it takes 7-8 seconds.

Are there any know issues with accessing Excel 2016?

The code is attached, any suggestions are appreciated.