Thank you for clarifying the used theme, this was indeed the missing part to reproduce the issue.
I can confirm that this is an issue with the current version of Kendo UI Grid.
I created an issue in our GitHub repository and forwarded it to our developers for fixing. You can track its progress at:
For now, there is no available workaround, if one is found it will be added to the GitHub issue for reference.
Additionally, I updated your Telerik points for bringing this to our attention.