Villagers Drown when standing in water block

Running a Minecraft server on win10 machine with 4 users.

 

I built a Docm77 style iron farm. I've noticed the villagers keep disappearing from the system.

I have seen a villager die for no reason while I was working around him in the day light.

 

checking the console logs for the server it reports that a villager had drowned at the time time it died.

 

even though they are standing in a single water block somw how they are drowning. it i

so far it seems random and low frequency. maybe an hour 1 will die.