Shulkers should not take fire damage. When they are hit with a fire aspect sword, or a flame bow, the shulkers will catch on fire, this does not happen in java edition though. This bug was fixed in a previous update, but then later reintroduced. Not only is this a parity issue, but it makes fighting shulkers more annoying as well. The shulkers will teleport when they take damage, and because of the fire, they will teleport all over the place, making it harder for the player to find, and kill the shulker.

To reproduce, simply attack the shulker with a fire aspect sword, or a flame bow.