sergei wrote:

> SSL_accept: Peer suddenly disconnected

That's it.  The client that was connecting stunnel did not negotiate SSL,
but closed the connection instead.  Stunnel sent RST packet to let its peers
know about this problem.

In your case BIG-IP incorrectly assumed TCP RST on an established connection
indicates a server problem.  It is an obvious bug in BIG-IP software.

Here is the workaround for you: