We had this fixed by your team a few months ago. Tried to update to Membership 2 and the latest Events+ but all the failed as the old data would not import. We restored site back to Membership Pro and had to reinstall Events+ from a pervious version we got from your site.
Now the issue of Attendees dropping down to No, not Attending is back . This is the previous support item on this: https://premium.wpmudev.org/forums/topic/events-dropping-premium-members-to-no#post-878213