So this just started happening to me last night in 1.14.1. I loaded into my realm on my Xbox One S (I normally play on PC) and my entire seed had reset itself. I went to my PC and it was the same. Attempted loading backups and every single one of them is missing entire chunks out of the world. I also spawned with an empty inventory. I have worked very hard on this world and until this bug hit me, I hadn't died once.
I see that this has been open since July and currently doesn't have anyone assigned. I'm wondering if I should just write this up as a loss due to a poor update and cancel my realm sub all together.
I should also add that I have not yet loaded this world from mobile since this started happening. The first instance of the bug occurred on Xbox and carried to PC.