I forgot to note that:
We have verified cases of mishandling of the response to separate requests which are close (< 1 sec) in the time domain.
The issue is quite rare (about 1 over 10 million of requests) in our environments. Yet the impact of the resulting mishandling is very disrupting.
Which version of mod_jk?
mod_jk version 1.2.26
When this event happened (wrong response) we noted that the response returned to client is the same that the very thread produced in the previous request execution.