Hi Tomas,
Thanks for your update.
We suspect that you are using the older version of Syncfusion.SfChart.WPF assembly. The reported problem has already been fixed in our latest product version.
So, we recommend you to upgrade to our latest product version(v15.1.0.37) to resolve the issue.
If still issue reproduced in current version, please share more information about the issue. It would be helpful for us to serve you better.
Regards,
Devi