Hi Singulus,
Thank you for posting your query to us.
I am afraid that I was not able to reproduce the issue. I have created a simple sample to test this issue and it is available in the following link.
http://websamples.syncfusion.com/samples/Tools.Windows/F71513/main.htmPlease have a look at the above sample and if still the issue exists, could you please try reproducing it in the above sample or send us a sample showing the issue and send us the reproducing steps so that we could sort out the cause of the issue and provide you a solution?
Regards,
Jisha