Email attach error

[Asoka]

We've set allow ANY ANY rules on the firewall of the PFSense Box, which we've had to leave enabled because we do traffic shaping on the box. However, something is causing issues when uploading files (small or large) or submitting form data on certain sites, so far all sites are SSL using port 443. For example, uploading to dropbox.com or slack.com does not work, it will sit there and then time out, same with Gmail attachments.

There is NOTHING in the firewall logs, or any other logs for that matter, which leaves me to believe that it's not the firewall blocking (not to mention the ANY ANY rules), but I've got no idea what other settings I should be looking at to see what could be causing this. If we remove the PFSense box from the equation (make the firewall the default gateway) everything is fine.

Does anyone have any ideas of what I could check out? I did a packet capture, however I'm not too knowledgeable in what to look for, but it looked like all the communication was one way, USER PC -> website, with no replies coming back.

UPDATE: Upon more testing any files smaller then 50kb get uploaded just fine, as soon as you pass that 50kb file size they will not upload.

Thanks in advance.