World progress deleted and world becomes the same as when first generated exept for inventory when going into past versions from 1.15.2

World loaded into past versions starts the world over and deletes everything except inventory. my whole build-test world is ruined now. this is a really important one to fix. I was going from 1.15.2 to 1.14.4 and then again from 1.15.2 to 1.14 and the same thing.