While AFKing my iron farm overnight, I found that the three villagers in one of the silos had all been converted to witches even though there was a layer of glass covering them. Later on I found that several more villagers that had been in the top level of my villager trading hall had also been converted, despite being covered on all sides by cobblestone.

What I expected to happen was...:
I put a roof over the villagers to protect them from lightning. This worked quite well until now.

What actually happened was...:
The villagers were converted to witches even though they had a roof over them. I also received the "Surge Protector" achievement sometime while I was AFK.

Steps to Reproduce:
Unfortunately as I was AFK at the time, I do not know the exact steps to reproduce the bug. However I went to a creative testing world, and when I stood on top of a one-block-wide roof above a villager and used "/summon minecraft:lightning_bolt", it was able to consistently hit the villager and transform it into a witch. This effect occurred through both glass and stone. A single strike also effected villagers up to 5 blocks away, and through walls. A roof of 2 blocks thick or more was successful in preventing the hit.