When the server is in its Full capacity or High capacity (most times when the server is online a fill hours after restarting and it get worse 1hour before the restart), it is almost impossible to play. The lag, sometimes, do not let us open a door or kill a zombie wit an axe.
I think the problem is with who is hosting the server (Fragnet).
I do not think it is problem with my internet, because it happen with all my friends.

Game version: 1.11.153728

I am sending a little video to show how is the lag. At 0:17 seconds and 0:29 seconds we can see my friend trying to walk, but he is teleporting (too much lag). 0:57 seconds I open a door.