So my sister and I have been playing together on Minecraft Windows 10 (I'm on the computer) and Minecraft Pocket Edition on Kindle, and lately we have been noticing that mobs in the distance disappear for a few seconds and then reappear, even when playing by ourselves and not on multiplayer with each other. Today, the issue has gotten worse. While playing on my world (note that I was not on multiplayer while doing this) that I just made, I started off as just chopping down trees, attacking sheep, mining a little, and then having a furnace, chest, and crafting table and bed. I had seen one or two mobs (a sheep and a chicken) disappear and reappear in the distance but I knew it happened. There is a sheep that always is around where my "home" is, and when I approached it (I was about a block away or so), it disappeared and did not reappear. I stepped back, but it still was gone. I went a little more back and stared at the ground for about 5 seconds until I looked up and it was back. There was a nearby island with two chickens on it that I wanted to breed so I started breaking grass to find seeds. I got the first one, but when I broke some more grass and another seed popped out, when I walked over it to collect it, it disappeared and did not give it to me. After finally getting both seeds (I had to look elsewhere, I tried several times to pick up the seed when it reappeared but it didn't work), I went to the chicken island to breed the chickens. But when I got close to the chickens, they disappeared. After around 5 minutes of attempting to breed them before they disappeared, I was able to breed them. When I started leaving the island, I passed right by one of the chickens who was in the water, and it disappeared but I could still see the bubbles the water makes when an entity is in it. I also passed by and through two sheep, and then went mining for iron. When I broke the iron blocks, they fell to the ground and disappeared. I walked back, did the thing where I stared at the ground (or opposite direction of what disappeared) for five seconds (I tried less, but they didn't reappear until it had been 5), and they reappeared. I tried to pick them up again, and I couldn't because they disappeared. I continued walking away, going back, restarting the game as well as the computer, but nothing has worked so far.