Bitdefender blocking Outlook IMAP sync to Gmail without displaying errors

My system has exhibited seemingly random issues syncing Outlook to Gmail through IMAP. I copy email (using Move --> Create a copy...) from one account in Outlook to a Gmail account configured in Outlook to sync by IMAP. Often, this works fine and the emails appear in the Gmail web interface. I've only been using this method for less than a week, but it has generally seemed to work fine, with maybe a minute or two of lag. It stopped syncing for hours the day after I first set it up, but whatever the problem was seemed to eventually correct itself. I tried everything I could think of and spent hours with Google support but couldn't resolve the issue by intentional steps.

I encountered the issue again today. Emails are copied in Outlook and appear in the Gmail Inbox in Outlook. Outlook says it has synced Inbox and completed a send/receive of all folders. No errors are noted by Outlook, and I do not see any messages in Bitdefender that it blocked any traffic. After trying the basics (checking for Windows Updates, installing and rebooting), I finally tried uninstalling Bitdefender entirely. Suddenly, the emails are appearing in Gmail (web interface)!

Are there troubleshooting measures I should try to fix this? If not, I suppose I'll just have to give up on Bitdefender and move on to a different product.