Checking something… My manual cache responds so poorly I can’t even view any of the settings now under the View button in Options, General, Data.
Maybe someone else who has a better working copy of the Manual Cache can help you out. Otherwise I imagine the standard recipe would be to uninstall and reinstall a fresh copy of MSFS. Sorry I can’t better help you out. I’m just an ignorant newbie with dysfunctional manual cache myself.
Have you checked the guide to the manual cache settings: [HOW-TO] Create and Manage Manual Cache Regions. The guide has links at the bottom to a number of other discussion threads that have cited the guide thread. Maybe posts in some of those other threads could help you out. Alternatively, Sartanius, the creator of the guide, helped out someone with a sticky problem in one of the threads. Maybe he can best suggest what you might do, certainly being an expert on the sim caching system as compared to me.