When using /fill command rotated blocks such as Stair blocks / logs / pillars etc. loss their orientation then changed to another block type.

Example! A east facing stone stair block will default to facing south when changed to a stone brick stair while using the /fill command to change the stair block type.

To reproduce: Place stone stairs in multiple directions then use /full command to change them to stone brick stairs or any other type of stairs. All will be replaced but all will be facing south.