@galaxy_2alex, first: i searched for a duplicate but couldn't find it, sorry.
Second: that affects version 1.8-pre3 and this affects MC 1.9
Even if you don't dismount the boat, the squid will get stuck.
F5 also doesn't work, I don't know about other buttons.
That worked! Thank you. You can close the ticket if you ask me.
I just click save and quit to title, en then press the red cross in the top left corner
First I executed "/worldborder set 9999"
then the rest of the commands.