Your question has already been answered in the support thread you have opened. Nevertheless I am copying the answer here in order the community to benefit from it:
If you are triggering the custom filtering functionality in an event like NodeCheckedChanged you should enclose the filter reset in a Begin\End Update block. This will trigger an explicit nodes update and the filter will be applied again:
If you have any questions, please do not hesitate to contact us.
Check out Telerik Analytics, the service which allows developers to discover app usage patterns, analyze user data, log exceptions, solve problems and profile application performance at run time. Watch the videos
and start improving your app based on facts, not hunches.