This is linked to my previous post.

I open in my Excel app sequentally other workbooks (currently in same instance), do something, and then close them. After the workbook is closed, the VBAProject of closed Excel file remains displayed in VBAProject window of my App.

Does this mean, that those closed files are using up some of RAM? Because the number of files to be processed this way is currently about 1000, and my App crashed after ~300 of those secondary files were processed.

(As afterthought, when this is the cause, then I probably have to open all secondary files in separate instance, and to clear this secondary instance every time a secondary workbook is closed there)