Worlds Reset

This has been a issue scine 1.15, when I load older worlds in newer versions, all my progress is resetted. Everything I had in my inventory is gone and all things I built is missing, it is in the same state as what it was when I first spawend into the world(s). It usually affects super flat worlds, but some infinite and old types aswell, this is a really huge issue, I am afraid opening older worlds, because I don't want more worlds to potentially be resetted. This has happend on more than one device (Tablet Android 5, Minecraft 1.15 and Phone Android 8, Minecraft Beta 1.17.20.22).