HTTP::payload from POST with different results

Hi everyone

I set an irule that logs the payload of a POST request (sent by a form from sharepoint).

If I submit the form from firefox, i can see the entire payload on ltm log, but if i submit the same form from chrome, i can only see a part of the payload, and in fact, if i do a check on the payload (ex. if http payload contains string) the check works on firefox, but not in chrome.

How can be possible?