The error you are getting may be related to concurrency problem which we have previously investigated.
It can be fixed by restarting the application or I can suggest you as workaround ( based on our knowledge so far ) is to set the property "Enable data caching" to False
which should limit such errors to 0. The property can be found under the Data section
of the Administration -> Settings -> Advanced menu
the Telerik team
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items