Hi, 

I have a site running version 2015.1.225.1 that has worked up until 1st January 2021. Now I am getting several javascript errors related to  

Telerik.Web.UI.WebResource.axd

with the following errors:

net::ERR_ABORTED 500

Any suggestion on what it might be? 

I have not done any changes to this code for many months (perhaps a year) as we are moving our customers over to a newer version (which means I have little to no knowledge how to find and fix this problem). We still have a few customers left on this site and they are now unable to do their work because of it. All I need it a quick-fix/workaround that might work for the next 2 months.  

Hello Terje,

We do not have access to the Telerik assemblies that you use in your project, so there is nothing we can change that will affect your application. 

I can see that you have blurred the domain in the URLs so I assume you are not using the Telerik CDN, which is the only thing that we could change that might affect you. 

With that said, I recommend checking any changes that are made to the server and especially server certificates that might be expired, e.g. SSL certificate.

As a temporary workaround, you can try enabling the Telerik CDN so that the requests for scripts and styles are to a CDN, not your server.

• https://docs.telerik.com/devtools/aspnet-ajax/controls/scriptmanager/cdn-support/overview 
  • https://docs.telerik.com/devtools/aspnet-ajax/controls/scriptmanager/cdn-support/custom-cdn-provider
• https://docs.telerik.com/devtools/aspnet-ajax/controls/stylesheetmanager/cdn-support/overview 

Also, keep in mind that there are many issues related to HTTP2, so if it is enabled for your server, you might consider disabling it and fall back to HTTP1.1:

• https://www.reddit.com/r/sysadmin/comments/7ijnpo/anyone_had_issues_with_http2_on_windows_server/ 
• https://help.goacoustic.com/hc/en-us/articles/360052067413-Disable-HTTP-2-in-IIS-10 

Regards,
Peter Milchev
Progress Telerik