Witches are not spawning

I tried making a witch farm at a witch hut. There were no witches spawning in the hut before i made a farm, and there are still none spawning. I hung out there for days before and after making the farm,none have spawned. Please fix this bug!

Edit: Made a second witch farm at a new witch hut on the same world. Same problem, no witches spawning before or after it was made. Maybe a bug when transferring a world from console edition to pe?