Jazz musicians don't mind a "happy accident" from time to time - as anyone might - but playing the music well is just as rigorous as playing any other kind of music and demands just as much practice and technique. Perhaps even more so, because the essence of the music is to take a melodic line or a harmonic progression and make something different out of them on the spot while keeping within the bounds of the tune... A shitty, wrong dischord is a shitty, wrong dischord whatever you're playing!

Dave - forgot to ask: do you stumble at the same places, or is it random stumbling? If the former, then it's important to isolate those sections and go over them very carefully for phrasing, fingering, etc.