Sheeps and axolotl randomly disappeared

I am extremely tired of this bug. I had some sheeps of every color and some axolotls but sometimes some of them disappeared, and this bug happaned so many times. My axolotl keep disappearing, so one day I decided to get some new axolotl, after I while i got some, and these are the axolotl that i had: 2 pinks, 2 cyans and 1 yellow, and then, after a while, guess what happens? A lot od axolotl disappeared randomly and I had only 1 pink and 1 cyan, I was extremely angry because this happened so many times and I was incredibly tired of this stupid bug. Same thing happened with my sheeps, one day I entered my world and I went to the sheeps and, almost EVERY sheeps disappeared and they couldn't escape, I built 2 blocks high fences and no carpets, and this happened a lot of times, before, I had sheeps of every single colors, after, I only had 3 lime sheeps, 2 or 3 white, and 1 light gray. I took so much time to get new sheeps of every color, but I couldn't get the brown one because I didn't had brown dyes, when I got the brown sheep it just spawned naturally. Since I named always my axolotls you can't image how many name tags I wasted from this bug. I must wasted over 15 name tags from cause of this stupid bug. Today all my white and green sheeps disappeared. I wasn't that mad because I wasn't really interested about these colors, but this doesn't mean you can make my sheeps randomly disappeare, just fix this instead of adding more useless things (apart from candles, I love candles).