The issue is reproducible when the `AllowCustom` parameter is set to `true`.
Typing rapidly in the input field of the MultiColumnComboBox component causes the entered text to blink. Also, some of the inserted symbols are cleared.

Reproduction (if bug)

Open this demo: https://demos.telerik.com/blazor-ui/multicolumncombobox/custom-values

Try to input text rapidly into the input field.

from this screenshot from the demo selecting a value via the keyboard leaves the box blank

to replicate press the down arrow when MultiColumnComboBox has focus

In the MultiColumnComboBox with the Data parameter, filtering and having only one element in the popup results in the popup closing when Tab is pressed, and the item is selected.

This behavior is not replicated in the MultiColumnComboBox with OnRead.

When the MultiColumnComboBox columns are rendered with a foreach loop, the component doesn't remove columns that are no longer defined.

The workaround is to recreate the MultiColumnComboBox: https://blazorrepl.telerik.com/wSOIvzvR46lEZrwy43