Incomplete Syncing MS Outlook 2011 with Gmail

I am trying to migrate POP emails to my IMAP Gmail in Outlook 2011. I have created the folders (labels) in Gmail, and then am trying to drag and drop the emails into the folders once they have propagated to Outlook. This worked brilliantly for the first 5 emails I dragged and dropped, and I was able to see them in my Gmail browser. HOWEVER - subsequent emails that I dragged and dropped successfully copy to the appropriate folder in Outlook, but they do not propagate to the Gmail folders on my Gmail account as viewed through the browser.

Outlook is seeing them in the Outlook folder, but it doesn't actually sync the folder, even though its says 'Folder up to date'. Somehow it is seeing it that these emails are in the folder and unsynced, but when I try to sync it goes very quickly to 'Folder up to date' rather than doing the syncing process bar, where you can see that the emails are indeed syncing.

Any advice would be greatly appreciated, I really need to preserve these emails for access on multiple Outlook systems.

Thanks in advance.