The index link is in my signature in red.

Even if you set the object variable = Nothing that will not destroy an Office app reference. Then depending on how the code was written you may be creating additional references unknowingly.

Yes, that does make it hard to debug when its a good sized app. I would say to first start on all the Dim's and dimensioning of Excel object variables. They should be fully qualified and not just "Dim oRange As Range". That will create the implied extra reference. Whereas if you went "Dim oRange As Excel.Range" its explicit and no extra reference.

What does your "Imports" look like? Are you using the .Interop or the .Core?