Björn Goetschke

Just out of curiosity Björn, was the world created in 15w45a or a prior world? Shouldn't make any difference, just interesting to know.

Created in 15w45a just for the test.

Tested in 15w45a with a 3x3 area enclosed by fences and a bunch of randomly spawned animals inside. Bug still occurs, simply logged out and in again and some animals got on the other side of the fence. Definitely no graphical glitch, i was able to lure the escaped animals further away with the appropriate food.

This bug is still present in 1.4.5.

It seems that the mobs can escape through all sort of blocks that do not cover the full block space, like fences, doors or glass panes.

I think the problem is, like Nicholas Williams already mentioned, that the mobs are running "into" the fences and when the chunk is unloaded and later reloaded the game can not say for sure from which side of the fence the mob was coming. So in some cases the game guesses wrong and the mob escapes.

Maybe the game just compares the integer values of the mob position with the positon of the fence block, without the fractional digits.

It is definitely not the same bug as MC-2025. As Marios said in MC-2025 the mobs really get out of the fenced area, in this case they are "only" visually glitching through fences, doors and other type of blocks that do not cover the full block space.

I think this bug is more of an annoyance and MC-2025 is an actual bug.

This bug is still present in 1.4.5, just tested it (overcrowding a fenced area with sheep).