When I open the chat menu, all of the customise options clumped together in the top right (as shown in attachment). When this happens, I'm unable to exit chat, type anything in chat, or actually customise anything. This means the only way to fix this issue is to restart the entire game, or to get hurt (which is quite hard in creative). Which then only just gets rid of the menu until you open it up again, where the issue occurs again. This means I'm unable to spawn things such as command blocks, and I have to use the pause menu for changing gamemodes and commands. This occurs on experimental and non-experimental worlds, and on Xbox One and Windows 10. The issue does not occur on official servers, and I have only encountered it on personal worlds.

Update from BDS-3994:
It appears to only happen on my worlds which were made before the chat update. If I create a new world, it does not occur.
However, If I copy the world it still seems to happen.