I know this is a really old thread, but I want to confirm this is still happening. I refreshed my token less than a month ago, and got the dreaded 400 sync error overnight. I now have to keep a smart list of people who have a program status of Webinar > Registration Error just to know when the sync is failing.
I have confirmed with Marketo that the random disconnects are a bug, and the issue has been escalated.
In the meantime, we just ran a webinar in EMEA this morning and I didn't know the GTW connection had disconnected with the 400 error, so none of the attendee statuses got updated in Marketo. Is there a way to force GTW to update statuses? (push the data to Marketo). Or do we have to manually export the list from GTW and import the status updates to Marketo? Such a pain.