Today, I decided to upgrade my Minecraft world to 20w22a from 1.15.2. It had 146 loaded maps, not all of which have consecutive ID's. When I loaded the world in 20w22a, some, but not all, maps were overwritten. When I try to /give myself those maps, it gave me maps that were previously empty. When I used "pick block" on the maps or checked the data folder for the world, some maps (including those that were not previously loaded) seemed to be overwritten.  However, not all undisplayable maps (including map #0, shown in the picture) were overwritten. Reloading all chunks or reloading the world did not help, and in fact, additional maps were overwritten or created whenever I reloaded the world.