Hi Julien,

I have thoroughly investigated the provided Dojo sample. What I have found out is that the jQuery library have made changes regarding the calculation of the height of the elements. You could check it out in the following article:

https://blog.jquery.com/2017/03/16/jquery-3-2-0-is-out/

Therefore, the issue could be replicated outside of the context of the Kendo UI widgets. If you change the version of the jQuery you will notice the different outputs in the console of the browser.

https://dojo.telerik.com/iVOWOnIN

On your behalf, I logged an issue in our feedback portal at:

https://feedback.telerik.com/kendo-jquery-ui/1456344-height-of-locked-content-in-treelist-not-calculated-correctly-with-jquery-3-4-1

And a GitHub issue at:

https://github.com/telerik/kendo-ui-core/issues/5643

As a temporary workaround, you could use the approach that I have provided in the following sample:

https://dojo.telerik.com/AkEqEvOq

As a token of gratitude, I have updated your Telerik points accordingly.

Regards,
Tsvetomir
Progress Telerik