You will see this messages in the url_response probe at loglevel 5:
Line 269172: Oct 4 11:43:52:020 [8672] url_response: [https://xxx.com.co/]: curl_easy_perform - Failure when receiving data from the peer (56)
Line 269173: Oct 4 11:43:52:020 [8672] url_response: [test_url] failed: Failure when receiving data from the peer (56)
Release : Any UIM Version
Component : UIM - URL_RESPONSE
The error codes returned by the libcurl library can be found at:
http://curl.haxx.se/libcurl/c/libcurl-errors.html
This seems to be a proxy server configuration issue.
Consult with your Proxy Administrator to check/fix/allow this URL's.