Hi luknowak,
Thanks for using Syncfusion products.
We are afraid that we are not able reproduce the issue "" from our side. We have attached the sample ,which we used to reproduce the issue, in the below link.
Sample link:
SilverlightApplication_TemplateMarker.zip
If the above sample does not meet with your sample scenario, please modify the above sample to reproduce the issue and revert back us.
Thank you very much for your patience.
Please let us know if you need any clarifications.
Thanks,
Manikandan.M