I copied all my items that have attachments to a different vault. Then in my Primary vault I moved those items to the trash and emptied the trash. This was done on Windows 10 free version.
I sync'd on my android app and confirmed that they have all been removed.
Back in Windows, I copied the items with attachments back to my Primary vault.
I sync'd on my android app and the issues still persists.
(NOTE: on the android app, in the other vault that I copied my items to, I was able to open the attachments [they are images]; so, I think this means something is messed up with my primary vault.)