After restarting the Server the following lines apear in the console :

• [92mStarting game server now...[0m
• Wed, 13 May 2020 20:10:44 +0200: Starting game server
• Script started, file is /dev/null
• [18:10:50] [main/ERROR]: Unable to bootstrap registry 'minecraft:entity_type'
• [18:10:51] [main/ERROR]: Unable to bootstrap registry 'minecraft:feature'
• at java.util.LinkedHashMap$LinkedEntrySet.forEach(LinkedHashMap.java:671)
• at gl.a(SourceFile:132)
• ... 11 more
• at cqg.<clinit>(SourceFile:77)
• at cif.<clinit>(SourceFile:64)
• at gl.<clinit>(SourceFile:131)
• at aoc.a(SourceFile:144)
• at aoc.<clinit>(SourceFile:150)
• at ckx.<clinit>(SourceFile:23)
• at cka.<clinit>(SourceFile:64)
• at bqk.<clinit>(SourceFile:9)
• Exception in thread "main" java.lang.ExceptionInInitializerError
• Caused by: java.lang.NullPointerException
• at bsh.<init>(SourceFile:44)
• at net.minecraft.server.MinecraftServer.<clinit>(SourceFile:179)
• at gl.H(SourceFile:94)
• Script done, file is /dev/null
• [92mGame server exited successfully...[0m

After that the server has a complete shutdown.

Restarting the server does not affect this problem.