Hello red51,
1. The following warning appears in chat:
WARNING: world could not be saved.
2. Found in the log file the following message:
========================================
Unable to save chunks (DT_0): 36, 36
java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901)
at java.util.ArrayList$Itr.next(ArrayList.java:851)
at C.a.a(SourceFile:202)
at D.p.execute(SourceFile:40)
at z.b.run(SourceFile:24)
=========================================
Hope you can help 
Greetings, Fabienne
