Thank you for contacting us and bringing this to our attention.
We reviewed the mentioned code and indeed it looks like it has a typo error. We have already implemented a fix for it and it is being tested by our QA team as we speak. If all goes well the fix should be available in our next internal. As we weren't able to observe the scenario on our side could you described to us in more details the required steps which lead to an exception when calling the RamoveFromParent method. This would help us validate all of the use cases where the typo could be leading to an issue in the RadDocking control.
I updated your Telerik points for bringing this to our attention. If we can be if any further assistance please let us know.
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