From the provided screenshot I noticed that you are using Bootstrap 3 along with Kendo UI. In order to successfully achieve the integration of both frameworks in a project, please follow the steps described in the following article:
Important to note is that Kendo UI uses the default content-box box model (box-sizing CSS property), while Bootstrap uses the non-default border-box model and applies it to all elements on the page, including the ones that are unrelated to Bootstrap. This breaks the layout of the Kendo UI widgets, which are placed inside a Bootstrap grid layout. To fix this, a simple CSS patch needs to be included in the layout of the application as described in the following section of the above-linked documentation:
Could you try configuring the application stylesheet references according to the above, remove the additional resizing logic, apply the Bootstrap box-sizing fix, and then test the MultiSelect widget? Let me know if this resolves the issue.
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