When playing Minecraft Bedrock on xbox one and your disconnected from the internet or have your console set to offline mode (settings/network/go offline) you will be signed out from your xbox account when starting Minecraft

Steps to reproduce:
1. Either disconnect your xbox from the internet or more easily set your xbox into "offline mode" (open xbox settings go to network and then select "go offline"

2. Start Minecraft Bedrock (you must be signed into a xbox account)
3. When loading the game you should be signed out of your xbox account