I have a client that uses a UDMP that was installed last November and has worked well since.
Configuration of the network protection allows Content Filtering to be enabled so the Work Option was enabled from day 1.
About 3 weeks ago the client started to have major issues accessing certain sites. these included Amazon UK, Lloyds Banking and Pinterest. These are critical sites for the business as they are a web based clothing company with huge exposure on the internet.
I could not pinpoint the issue immediately as for everyone outside of their network the sites loaded as expected. Eventually I decided to disable Content Filtering and the sites started loading without issue.
I have now had to leave off the Content Filtering on the UDMP for fear it will block other legitimate sites, but of course this is not a great option particularly in a business environmant.
The lack of logging and end user warnings meant tracking the issue was not straightforward and the lack of granular control of the filtering equally frustrating as we cannot whitelist good sites irrespective of the settings. Users where left looking at a white screen. A warning about the site being blocked would be far more informative.