zombies wont climb stairs

Unable to replicate.

I went back to 15w51b and confirmed that I still see the same thing
not sure what other info is needed, I attached a screenshot

I cannot replicate this at all.

My daughter pointed out that the zombie spends most of its time looking toward a village with villagers, but this dint happen in older versions, I will try killing them all

killed all villagers and still the same thing

I have found that the zombies will climb some stairs, but in older versions they climbed these stairs too
I tried eliminating the redstone next to the path, didn't help

I removed all stairs and rebuilt it one block over, no change

with the villagers all dead, the zombie does not wonder away, but still wont climb

made a test case with stairs in each direction: the zombies would climb east and west facing stairs, but not north or south facing stairs

made test case with no stairs, and zombies would climb up block paths east and west, but not north or south