Doubts related to the response timeout

Good morning,

I am having some issues defining the response timeout of my webservices.

I have set the value response timeout to 20 seconds.

The failure timeout is set to 20 seconds also in order to avoid Ensemble to make retries.

I leave a screenshot of the configuration:

I have this configuration in two webservices. 

In one of them, I observe that some requests give timeout at 20seconds but others give timeout at 40 seconds. The next screenshots show the difference of time between the point 3 and 4. 

On the other webservice, I observe that some requests give the timeout at 20 seconds, but there are others that do not give the timeout and the request is resolved after this period of 20 seconds. Next screenshot shows an example of this. The timeout is set to 20seconds. However, the request was resolved after 31 seconds.

Does anyone know how to fix this in order to avoid requests skipping the defined timeout?

Thank you in advanced.