I have been experiencing a hard to track issue in my software, but I have managed to reduce it to its bare basics.
There seems to be an issue with the files E.xlsx and I.xlsx, they load fine individually but when they are loaded one after another with other files the software aborts with a System.NullReferenceException: 'Object reference not set to an instance of an object.'
Please see the attached code and files.
Any help or advice would be really appreciated,
Darren