The flat world bug is broken into invisible

hello Mojang. I am one of the developers and builders of mcpe maps. I built my map on a flat world within 1 year. but after i update to official version 1.17.30, the map becomes invisible (map with experimental cave and cliff). please fix this bug. if the flatworld coordinates to -64, please set the rendered snippet at 0/coordinates normal as the previous version. hopefully it will be fixed quickly and I can continue the map in the latest official version..