Confirmed for 20w19a
I think, that the worldborder was crashing my world.
The world with the datapack:
https://drive.google.com/file/d/15OinIqT3T5XVIV3dyKhUpSX9oAfsdJtF/view?usp=sharing
https://paste.ubuntu.com/p/GJCh6QSNHF/
Ok!! thanks for the tips.
Confirmed for 20w19a