I found that I cannot join some certain people's worlds, but I can still join rest of them. I thought it was just some internet problems until some people told me they can't join my world either. It affects about 1/2 people.

How I try to fix it:

1. In the begining, I installed Minecraft in C drive. A firend using PS4 and another one using Win10 are not able to join my world, but the other one using IOS device can join it.
2. I reinstalled Minecraft in D drive via Minecraft Launcher, then somthing wierd happened. Win10 and PS4 can join, but IOS cannot.
3. I reinstalled it again in C drive, and it backs to 1.

I guess it's due to Minecraft Launcher, but I have no evidence. Does it happened to anyone else?