Although the 100% height styles, which you have set currently, do not work for two different reasons (see below), I must point out that using the k-animation-container and k-popup classes globally in the shown way is able to break all Kendo UI popups on the page or in your application.
Regarding your use case, please review the following example.
Why don't the 100% heights work?
1. You are trying to override inline height styles with external height styles without using "!important".
2. A percentage height requires an explicit height set to the parent element (Menu item), which is not set in this case.
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