Since upgrading kendo (layout was upgraded from 4.0 to 6.2) any modal which is being called within a tabstip-tab has issues where the fade doesn't go away. If I take the modal outside a tabstrip it works fine.
The currently described behaviour was intended in v6.2.0 as some additional styles required for the TabStrip component were added. The following answer contains a workaround by including a bit of additional CSS styles to bring back the previous behaviour:
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Something like this: https://github.com/telerik/kendo-angular/issues/1506