Discrepancies between local and online synched libraries

Hi, I have just bought a new Windows 10 laptop, and purchased Endnote 8 (I previously ran Endnote 7.7 on my old laptop). In order to import my existing Endnote library, I synched the new empty library to the online library, which contains exactly 2000 references with 1544 attachments. However, following completion of the sychronisation, my local library contains only 1995 references with 1552 attachments! There were no error messages. Can anyone explain the discrepancies, and how I can rectify them. I don’t want to have to manually scan through both libraries to uncover the anomalies. Thanks

Sync Details
Sync was last run: Thursday, August 24, 2017 at 13:50:32 PM +0100
Sync Status: All changes have been sent.
Error Code: None
Error Message: None

Local Sync Library
Library Name: My EndNote Library
References: 1995
Groups: 26
Group Sets: 1
Attachments: 1552

Online Sync Library
Username: xxxxxxxxxxxxxxx
Serial Number: xxxxxxxxxxxxxx (Premium until August 23, 2019)
References: 2000
Groups: 26
Group Sets: 1
Attachments: 1544 (2.63 GB)

Sync Limits
Number of References: 1000000 (998000 can still be added)
Number of Groups: 5000 (4974 can still be added)
Number of Group Sets: 5000 (4999 can still be added)
Attachment Storage: Unlimited

This is very similar to my sync results!  

Greetings Jhodgson65,

I suspect there’s a problematic PDF file attachment stored in your desktop EndNote library and that file is inhibiting EndNote from syncing the remaining attachments with your EndNote online account.  I’d suggest giving our Technical Support department a call, as we can walk you through generating EndNoteSync log files for further troubleshooting:

http://endnote.com/support

Typically, these logs that we’d generate would mention a specific PDF attachment that would need to be temporarily removed from your desktop library to allow for a complete sync to take place.