This is a regression since R3 2018 - GitHub issue.
The issue is reproducible when title is set as window tag attribute:
<
kendo:window
name
=
"mywindow"
title
=
"mytitle"
>
<
kendo:window-content
>
<
div
id
=
"warning-new-container"
>
Message
</
div
>
</
kendo:window-content
>
</
kendo:window
>
Workaround:
Instead of using title attribute, set the title through window-title tag:
<
kendo:window
name
=
"mywindow"
>
<
kendo:window-title
text
=
"mytitle"
/>
<
kendo:window-content
>
<
div
id
=
"warning-new-container"
>
Message
</
div
>
</
kendo:window-content
>
</
kendo:window
>