Bump and displacement are at 0 with black, not gray. The idea that gray is neutral keeps getting repeated (just saw it today) and that is incorrect.

The problem you had was that with a modest amount of bump essentially everywhere (gray) the creased surfaces crossed over each other.

If you're using a bump where 50% gray is supposed to mean no bump, (as in many other apps) then you must use a math node to subtract .5 from it first.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)