We are attempting to attach a document to an Opportunity. However, the document is going to a general Opportunity folder. 

 Hi Debbie,

We've tried this out and can't seem to duplicate the same.

Would you mind writing into our Support with a few more details?

Thanks.
Drew

Forgive me. We have re-tested on our end and cannot duplicate the same instance. Obviously, the problem was on our end (User error). Sorry.