Realm Plus kicks all players out continuously, subscription is not ended

Cannot play on my Realm Plus server. Purchased Realm Plus subscription 16 days ago. Purchased the whole game a month ago.

1) When I'm alone and playing in Overworld, it seems ok. Problem starts when I go to Nether. I cannot return from Nether: everytime portal doesn't work properly, I never see the Overworld loading page, instead it might be just me standing in portal or "Connection to server is broken" page and I get kicked out. When I go to the Realm server again, it uploads the process 5-7 minutes earlier before I got to the portal.

Example: I tried to leave all my stuff in the chest before stepping into the portal, and after the error page I went to menu and entered my game again. I was far from the portal with all my stuff on me. The game didn't remember my latest process. 

2) When I play with friends it's worse. Now Nether and Overworld kick us all out from the game, after returning each of us gets our old process.

Example: Today each time after kicking us out, the game returned us all to the same spot/process like a time loop. 

It started yesterday, when one of us had to go back and forth between Overworld and Nether. At first it happened only to the one using portal, now we get kicked out all four of us. It's not playable completely and I'm not willing to play at all if my friends cannot join. 

Since I'm only a month in the game, it's clear I don't use any mods. I don't even have additional content packs on. It's early stage of my experience with Minecraft.