Checking Persistence iRule

I suggest you uncomment the three log lines that are currently commented out, and see if that shines any light on what's going on.

There are two paths through that code that will end up persisting on SSL session ID, which is a disaster waiting to happen, since the SSL session ID can change as often as every few minutes, depending on the client.

You really should be persisting on something that is expected to remain static, like a session ID that the server passes back to the client as an HTTP cookie