Error receiving by a specific station in ASM:
(9501) Does not match 'We stop threats hiding in plain sight.'
Release : SAAS
If the monitored page is a Single Page Application, it means that at the point in time when the HTML code of the page is fully loaded and the onLoad DOM event is fired, the expected page content may not yet be present, since it's still being loaded by another, asynchronous HTTP request, which may finish at any later point in time.
By default, the Full Page monitor evaluates the 'Match string or regular expression' value against the page content as soon as the onLoad event is received.
Due to this, a content match error may be reported if the asynchronous HTTP request that downloads the page content takes too long to complete. There is nothing wrong with the Istanbul station, the page is simply loading a bit slower from that location. As you can see in the screenshots of your failed check, the content match failed because the page was still blank at the point in time when the page content was evaluated.
The solution is to enable the 'Wait for network traffic to stop' feature in advanced monitor settings:
This way, the content match evaluation will get delayed until all the open HTTP requests are finished, irrespective of the onLoad event.