The file in question is requested internally by RadScheduler. However it does exist and it's quite unusual that you are getting this message.
On fixing this... Since the resource is already there, and error is a false positive, you can try testing with a newer version of the control and see if that error pops in the log as well.
Or, if the error is not bothering you from appearing in the log, you can leave it as is until you are ready to upgrade.
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