Command Block Content Not Loading When Above y=255

When accessing a command blocks face that is aligned with the build limit, the commands inside the command block don't load. (Or take a very long time to load, I haven't managed to get them to though) In the first screenshots I'm playing on a singleplayer 1.15.2 creative world. In the last two I'm in 20w09a (The newest 1.16 snapshot). By side aligned with the build limit, I mean the top side of the command block when the command block is at y=255. The greyed out buttons show that the command block's content hasn't loaded. Th