This bug happens when you fly away from the chunk. It also happens when the game crashes and you go back into the world. The oak wood stairs were placed a long time ago.
Related issues
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[Mojang] Mega_Spud (Jay)
migrated
Does this bug affect 0.15.9? If so please respond.
migrated
This bug does not affect 0.15.9
This sounds similar to (if not the same as) the affects of MCPE-12347