The version that you are using is the last one that includes DLL files for .NET 2.0, so unless you migrate to a higher .NET version you will not be able to upgrade to a newer version of the suite.
The only thing that I could suggest for handling the problem with that unsupported version of our controls is to use the client object of the RadDatePicker
control and manually fix the popup position. In the help article below you can find how to get reference to the client object:
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