Problem only appears when filtering is turned to true. When I choose any value, and then I'm searching for another one, and delete back the letter, previous values are displaying twice. You can check this behaviour on gif which I've places below. Problem also exist on official example from documentation which I've also linked below.
Already selected values, shouldn't appear twice while filtering.
Demo on your website
https://www.telerik.com/kendo-angular-ui/components/dropdowns/multiselect/open-state/
Demo in my case:

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Browser:
System:
Seems like duplicate of https://github.com/telerik/kendo-angular/issues/1767
I'm still getting the same bug after upgrading 'dropdowns' to 3.1
@patrykp57 That's great ! You solved the same problem for me. I have another question ,How to have a triangular button on the right side ?

Thanks