Thank you for the patients.
After the report from the developers' team, I can confirm that this is an issue with the current version of Kendo UI TreeList.
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 in the GitHub issue for reference.
Additionally, I updated your Telerik points for bringing this to our attention.