corrupted World!

We are 2 people on a realm and blocks or chunks are constantly clipping and in completely wrong places. We have to keep downloading/replacing an old backup to get the world back to normal, but we lose important progress by doing so. It's been like this for 2-3 weeks and we can't find a long-term solution for it. Could you please solve this problem? Sry for my english, i am a german guy