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I find the reason: this happens only when column wp_posts.post_name containts %d8%a8%db%8c which is in persian بی , so by removing %d8%a8%db%8c from post_name it works. maybe mysql has problem in finding this collation.
in fiddler i can see that GET ahangbaz.com/1300/… HTTP/1.1 ----->>>> HTTP/1.1 301 Moved Permanently Content-Type: text/html; charset=UTF-8 Location: ahangbaz.com/1300/?-???-???? Server: Microsoft-IIS/7.5