Hey Senz,
you are right, seems like I should raise a ticket.
There are no BeforeSave-Events defined for subnodes in my solution, I also don't see a potential show-stopper with those events, even if they existed.
Unfortunately, I cannot perform "Dump Analysis" on UI/Silverlight exceptions. I think this is not supported for Partner Developers (which is a serious pain point for me). But anyway, this is not an issue in this particular case.
Thank you and Kind Regards
Pablo