Posts Updated, Levels Drop Them, Students Frustrated

I'm seeing a consistent pattern with the Membership plugin, which is this:

I updated blog post content, and the Membership Levels drop those posts. I've had complaints from users on my site, who are on different Membership Levels, so it's happening across the board: different posts, different levels.

Sure enough, I go in to check (after having to tweak the dates on the Posts to today so they'll show up in the Levels Post list of the most recent 25) and they are unchecked, even though I've documented adding them to that particular subscription level.

Why is this happening and how do I fix it? Thanks for your help!