I hope today finds you well.
Close out visual studio and stop your IIS processes. Create a fresh project in your current version, copy the Bin directory of the new project into the Bin directory of your current project. Open visual studio and build.
Rebuild may remove referenced assemblies from your bin folder (this is fixed in sitefnity 6.0 which will be released in april) and you either have to add them back to the bin folder or move all of the assemblie references from bin to another folder (for example 'lib') this way they won`t be removed during rebuild or the project.
I hope this helps.
the Telerik team
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