I used @onkeydown:stopPropagation on the MudRadio tag.

Their was MudNumericField inside the MudRadio wich was still triggering the keydown event, so I also added @onkeydown:stopPropagation on the MudStack inside MudRadio

<MudRadioGroup>
    <MudStack>
        <MudRadio @onkeydown:stopPropagation>
            <MudStack @onkeydown:stopPropagation Row>
                <MudElement HtmlTag="span">text 1</MudElement>
                <MudNumericField />
                <MudElement HtmlTag="span"text 2</MudElement>
                <MudNumericField/>
                <MudElement HtmlTag="span">text 3</MudElement>
            </MudStack>
        </MudRadio>/>
    </MudStack>
</MudRadioGroup