Passive mobs randomly stop following me sometimes when I hold wheat/carrots/etc.

First off, I used search, but I didn't know what to really search for, and all the results weren't this bug, so yeah.

Anyway, I was leading two cows with wheat, and they kept randomly losing me, and nothing could get them to go back, until they finally, and randomly, did. It was so annoying that I just killed them and /gave myself two spawn eggs and went back to my base...

Intended or not, it's really annoying, and should probably be changed. If it is intended, maybe make selecting something else and then wheat again could "fix" them?