I'm running DNN 4.9.5. I recently switched to disk caching instead of memory because I hoped it would boost my performance. I started having a strange problem where all the modules on a some pages were disappearing. It was not limited to a single type of module. It was only on some pages on the portal, and it affected all modules on a page. When I was logged in as host and tried to "add an existing module" on a test page, my missing modules did not show up as choices. I checked the recycle bin, and they weren't there either. When I looked in the database, the rows for my missing modules looked like the other rows in the tabmodules and modules tables as far as I could tell. The "is deleted" column was set to false.

"All users" already had view permissions on all of my problem pages. As I was experimenting, I happened to add view permissions to a problem page for an additional role. Suddenly my modules reappeared. Adding view permissions shouldn't really have changed things because all users already had view permissions. I think it just caused the application to take a fresh look at the page and realize "Hey, there are modules here!" Anybody ever see anything like this? When I searched dotnetnuke.com, it looked like there might be a realted issue 8117 on Gemini. However, when I click the link from the search page or try to search Gemini for that issue, I get a SQL timeout expired error.

Thanks for your advice, everybody. Happy New Year!