Ugh!  I'm so sorry for you.  I just gave it a try exactly as we did before and did not have the issue that we were having earlier.  

However, I changed my process so that I don't depend on QBO doing the right thing.  I keep a "File Explorer" window open and drag and drop files from it over to the "attachments" area on the Invoice in QBO.  I have the two folders "pinned" on my File Explorer window where the attachments are stashed until I do the Invoice so that they are easy to find. 

Steph