Tin Svagelj
Comments
It is a bug, maps don't keep their names after player spends experience renaming them. Furnaces keep their names, enchanting tables keep their names, chests keep their names, but maps don't. This is a bug. It is also one of those 1-minute-fix bugs.
I don't see why this shouldn't be fixed?!
Actually, this is /fill command not doing its job right. Fill command doesn't destroy old tile entities, just their blocks and since MC has custom renderers for some tile entities, old renderer remains.
As old tile entity remains in the same place and when placing another you create a new one, you end up with two tile entities in the same place and a new block which actually opens new GUI.
This is /fill and similar commands not (re)moving tile entities as they are supposed to.
Also, the reason this glitch resets after restarting the world is because Minecraft tries to validate tile entities when they load and see if their block is still there (which fill doesn't) and destroys them if their block doesn't exist.
It is weird however that /fill does work below 63. This is probably another bug that has to do with chunk update inconsistencies.