I certainly don't intentionally have multiple clients with the same ID but I'm sure it happens on occasion when I am testing and forget I have another browser open. That said, I just came back to this thread because I am seeing generally weird behavior at times, that really feels related to the usage of the id=XXX hack to force a specific session file. I'm adding a comment to that thread in hopes that there is some OTHER solution that doesn't involve "?id=XXX"