Word Request— word for fumbling and being clumsy with pronunciation

I was wondering for a long while, and I can’t seem to find the word.

I’m thinking of the way people, when feeling strong emotion, replace ‘r’s with ‘w’s, and generally are clumsy with their pronunciation.

Maybe, as I mentioned above, clumsy with words— but I feel that has another meaning.

I can do well with just explicitly telling them their pronunciation was tumbling all over the place, but I believe in the show don’t tell technique and wanna follow it throughout my writing.

Edit: trill?