I see that your project has some specific structure and I kindly ask you to open a support request and provide us with your project. The file attachments are limited to 20 MB, so you can send us an FTP account that we can use to get the project and observe it locally. We will attach it to our local performance tests machines and see if there are any glitches with our code or the issue is specific to your project. Then we will try to provide fix, suggestions, guidance how the issue could be resolved.
We made some performance optimizations to the latest version, so it is important for us to know if you are using it and if you have made an upgrade. We would like to know if you have custom controls, modules, code that interacts with global events and IoC.
I hope that I will be able to help you as soon as I see your ticket and some more details about this case in it.
the Telerik team
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system and vote to affect the priority of the items