Recently I was working on performance testing for one of my application and came across this issue where all of my call failing in JMeter.
I started analyzing and found it was a wizard where series of calls were on same page using ASYNC Ajax calls which were complaining “The page is performing an async postback but the ScriptManager.SupportsPartialRendering property is set to false. Ensure that the property is set to true during an async postback” due to which my main POST was failing with error “Invalid postback or callback argument”.
The strange thing was all of this was working fine when run via UI. Then started reading about when this error occurs and came across one discussion on a forum where they mentioned about SupportsPartialRendering is not supported by every browser.