Inventory resets after closing the game and rejoining Realm. Wipes inventory and replaces it with “old” inventory. I believe the blocks/items it replaces the inventory with are what my character had on them before switching the realm from version 25w31a to 25w32a. It also teleports me to where i logged out at before updating the realm version. This only happens when I have items/blocks in my inventory before logging out. Also the game needs to be completely closed after logging out of the realm for the bug to happen. Good Luck, and thanks from one tech to another.
After further testing it seams to happen randomly. Sometime it reset after going to main menu, some times you have to shut the game, some times it wont happen at all. I might be tied to how long before logging back into the realm.