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
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.
Open this demo: https://demos.telerik.com/blazor-ui/multicolumncombobox/custom-values
Try to input text rapidly into the input field.