Sorry about that, link for client logs :
BTW I wanted to say what happened with today's attempt to join the server.
I could move around in the world for about a minute, then the same error, BUT when I wrote a command in the server's line that teleported me to the first spawn location, again I could stay in the world and again about minute, this time I did not move even a step, and so I jumped out with error on screen.
Although I am on the remnants of the RAM of my computer but 1gb in the store should be enough I think (already ordered 8gb extention). Server has 3gb reserved, client 2gb, entering command "memory" in server gui pops up info about 700mb to1gb free space.