Server crashing at saving chunks

First I created a Spigot 1.18.1 Server Jar with BuildTools

Then I started The Server, accepted the EULA and so on. After it generated the worlds, I wanted to stop the Server and then it crashed.

Log: https://pastebin.com/RXqTM98F

The Server has no plugins, the only change I made is increasing the Timeout-Time in spigot.yml. As starting script I use:

/usr/lib/jvm/java-17-openjdk-amd64/bin/java -Xms4G -Xmx6G -jar spigot-1.18.1.jar nogui

Server has around 40GB free disk space