Witches do not spawn as frequent as they should in witchhuts

Witches should spawn a lot more frequent in the witchhut.
A witch spawns in my witch farm once every 3 minutes this is not what is used to be. They used to spawn every couple of seconds.

P.S. This bug appeared in 1.13pre-1 and pre2 I wasn't able to select 1.13-pre1 in the box above. But the bug first appeared in pre1