I created a new world (superflat with Roofed Forest biome) and flew around the map generating new terrain. A few of these errors appeared in the game log:
12:07:17 bey Failed to create block entity DUMMY
i: Non [a-z0-9/._-] character in path of location: minecraft:DUMMY
at oe.<init>(SourceFile:36)
at oe.<init>(SourceFile:41)
at bez.a(SourceFile:63)
at bey.c(SourceFile:72)
at bim.a(SourceFile:526)
at bim.a(SourceFile:97)
at sd.g(SourceFile:93)
at sd.d(SourceFile:146)
at bnt.a(SourceFile:225)
at bnt.a(SourceFile:78)
at bpv.a(SourceFile:16)
at bpv.a(SourceFile:13)
at bkd.a(SourceFile:27)
at auw.a(SourceFile:469)
at bjg.a(SourceFile:144)
at sr.a(SourceFile:12)
at sq.a(SourceFile:33)
at bhy.a(SourceFile:85)
at sw.a(SourceFile:54)
at sw.a(SourceFile:23)
at zt$a.a(SourceFile:143)
at zt$a$$Lambda$891/13133174.apply(Unknown Source)
at java.util.concurrent.CompletableFuture$AsyncApply.exec(CompletableFuture.java:501)
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:902)
at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1689)
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1644)
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)
Linked issues
relates to 1
Attachments
Comments 8

I didn't save the log file. I'm trying to reproduce the issue again so I can get a new log file.

I have successfully reproduced the issue by creating a DEBUG world. A log file is attached.
[media]

Please check if that's still an issue in the latest 18w20c development snapshot.
Can you confirm this bug still exist in 18w22c ? And if it does, can you send a world with the bug happening ? I couldn't reproduce it after generating over 1M blocks.
Still occurs in 18w22c, but I wasn't able to reproduce it every time. Created serveral worlds with the same seed and loaded the terrain in the same locations, but the error didn't always occur.
The world in which the error appeared once
[media]Thanks for the help. This bug is hopefully fixed in the next version
Please attach the full log file.