After extended testing I wasn't able to reproduce the issue that you have described. Could you, please, check if you are able to reproduce it on your side through the demo site as well - http://demos.telerik.com/aspnet-ajax/scheduler/examples/advancedformtemplate/defaultcs.aspx
? If the issue does not reproduce, then I will need a sample runnable project so that I can investigate the issue on my side. For that I should advise you to open a support ticket and attach the project there.
Looking forward to your comments and sample code.
All the best,
the Telerik team