Hi Maxim,
This is really odd and so far we have not received any customer reports that resemble this issue. Unfortunately based on the provided information we were unable to reproduce the problematic behavior in our local tests and we would not be able to advise you properly unless you are able to isolate the problem and send us a sample application that we can investigate or a step-by-step guide that we can use in our local tests.
We are sorry we cannot be of much help on this issue.
All the best,
Manuel
the Telerik team