Item Frame/ ALL entities Disappearing randomly

I have to apologize for making this for obviously their other bugs mentioning things disappearing but I haven't the slightest which one to go to.

I was working on something and then I ran back to where I was before and I saw my spawned mob disappear very abruptly and the whole screen slightly jerked. And that was when I found out how/why my (Invulnerable:1b) Item_Frame item frames were gone. The weirder part is that my single invulnerable item frame on the same location but behind a was of quartz was still there. Nothing ever happens to it. It's really bizarre. floating items seem to disappear a lot quicker/sooner/closer then they ever did before. I have had creepers almost about to kill me and they would just vanish right in front of me.