Error ut005028?

My users have been getting this error UT005028 followed by a Proxy unreachable/crashed, stopping it now, it happens right after the proxy is activated. It is somewhat intermittent, eg some users get it others don’t when it happens, they can’t access the application. It seems that it can be remedied by deleting cookies or using InPrivate/incognito mode.

UT005028: Proxy request to /proxy_endpoint/######/dt-ext-fixedheader-1.10.20/css/fixedHeader.dataTables.min.css failed

I can’t tell if it is related to an application, networking or security issue. I know datatables have compatibility issues. It might just be an issue with http requests though because datatables are the only ones that use http and ajax.

Are there any ideas how to trouble shoot or log this?