We have replied to you in the support thread you have opened, you can check our response there. For your convenience, please find a copy of our reply below as well:
"Please accept our sincere apologies for the inconvenience caused. It looks like there's a problem with this particular method(AddPageNodeAdditionalUrl()) introduced with our Sitefinity 4.1 SP3 codebase. We have addressed the issue and a fix will be provided in the upcoming Sitefinity 4.2 release. I would kindly ask you to wait for the official release to become available for download and upgrade a copy of your project."
If you have any additional questions, or need some further information, please let us know, we'll be glad to help.
the Telerik team
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