What is the actual bug?

It's a bit hard to see it but all people were in the air.

Can you show me your Game Settings?

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Can't really tell what happened there. Can you try to reproduce it?

Don't know actually. It just happens from time to time.

Are you sure that VBO mode is enabled? By the looks of the firecape on the first screenshot, it isn't. Do you get a warning when starting the client. Can you type ::openglinfo and show me that too? EDIT: Yes, that's the bug, it only occurs when VBO mode is disabled or not supported.