Animals will lose interest if forced to jump up or fall down a block.

Confirmed for 1.2.3.6 on Windows 10. If the mob has to jump up to reach the food, it appears to be unable to jump that high. It makes several attempts while looking at the player, falling back to its original position each time, then eventually gives up and wanders away. But a moment later it rediscovers the food and runs back, only to repeat the same behavior. If it happens to jump up the block while it is in normal wandering mode, it has no problem, and targets the player in the usual way.

If the mob has to jump down, it does so but then appears to have forgotten about the food. It may stare at the player or it may not. Eventually it notices the food again and targets the player, rushing until it encounters another up or down transition.

Even when they don't have to jump they lose interest as well. I use to have a herd of sheep and cows following me now they lose interest after a few seconds. Also if you give them wheat it will keep giving them until your inventory is empty that glitches back for every mop dogs sheep every mob you can just keep feeding them over and over again.

I’m having a similar problem on Xbox One where animals will not recognize the food at all. Occasionally pigs will but only for a second or two. In particular, rabbits will not recognize carrots whatsoever. So I am in a pen with them and they just ignore me and run al over the place. It makes breeding very difficult.

Yeah, I found this on Xbox One! I currently have 1.2.3.6, so I'm glad it gets resolved in 1.2.5.0! It's very annoying.

@Eric - This is very interesting. It describes the same problem as MCPE-28028, except that we haven't had a clear report before that it happens when you're inside the fence; in experiments, if you were inside where the animals could actually get to you their behavior seemed normal and it seemed to reduce the lag. You're not in the 1.2.5 beta update are you?

Helen Angel has reported on Reddit that this is scheduled to be fixed in 1.2.9. Of course, that can't be guaranteed; it's possible they could find out that the fix causes some other problem so they have to revoke it.

Lots of problems take months to correct, especially those like this where a lot of separate game mechanics combine to produce an error under very specific circumstances. Whatever gets modified to fix it has the potential to affect all the unrelated situations where that game mechanic comes into play, and those could be implemented by code scattered all over the codebase. To be thorough and avoid breaking something else, a developer has to find all those pieces of code and make sure they continue to work after the fix. If one doesn't, he has to basically start over figuring out another way to fix it. Plus, keep in mind that the code probably doesn't read anything like "here's what to do if a passive mob pursuing food has to climb up or down by one block". It's a behavior that emerges from the interplay of the code for an entity moving to a different block, the code for interpreting and prioritizing mob goals and behaviors defined in a behavior pack, the code for detecting a mob's preferred food item in the selected hotbar slot of a player within a certain distance, etc. In terms of auto mechanics, it would be like trying to tune an engine by calculating the result obtained from a certain composition of fuel in a certain proportion of air ignited in a cylinder of a certain size to push a piston with a certain amount of friction against a variable amount of resistance. Programming and debugging is hard.

But Helen Angel also said this 13 hrs ago on Reddit.

We fixed these bugs relating to spawning. We THINK this might fix the slime spawning issue but still have the bug open in case it doesn't.

Increased the spawn rate of animals to make them easier to find (JIRA 29536)

Creepers will now stop walking when they are about to explode (JIRA 29454)

Creepers will no longer explode after losing their line of sight of players (JIRA 27212)

Wither Skeletons will once again spawn in Nether fortresses (JIRA 16292)

Animals are now attracted to food if the player is outside of a fenced area or standing inside a Fence block (no JIRA number)

Animals can once again be lured over uneven terrain without losing interest (no JIRA number)

Note the last line about animals being lured over uneven terrain not having a Jira number. Surely it is this one?

@Morgwenna: That's the same post I was using, and yes, she was referring to this bug. But until 1.2.9 actually goes into certification, there's a small possibility that anything in it could be yanked because a problem is discovered. I was just being cautious when I said there was no guarantee; it's almost certainly going to be fixed.

Rabbits keeps running away, can't tame them.

the problem has been solved in version 1.2.9 for iOS