Suppose we have a Telnet check that fails to connect to the server:

27649:20140808:145806.246 Item [OpenBSD 3.9 - i386:telnet.run[long]] error: cannot connect to TELNET server: cannot connect to [[192.168.1.2]:23]: [4] Interrupted system call

Now, suppose there is another Telnet check after that tries to execute a long sequence of commands. It sends the commands, but since the machine is slow, it times out while reading from the server. Finally, it fails with the same last part of the error message, as returned by zbx_tcp_strerror() in telnet.c:456:

27649:20140808:145826.800 Item [FreeBSD 4.2:telnet.run[long]] error: No prompt: cannot connect to [[192.168.1.2]:23]: [4] Interrupted system call

It can be seen that the item's host is different, but the IP in the error message is the same. This indicates that the error from the previous failed check was used. Full log can be seen in "telnet.log" attachment.