Trying to get a tremolo

Finally getting around to sending my first TC after literally years of membership! I have included both an audience view and magnet view of me playing a scalar passage with my natural and very speed limited technique. I suspect I'm probably string hopping, because I've never been able to get 16th note passages must faster than about 110 bpm. In the other two videos, I'm trying to use the "tall mouse" position to play a tremolo on several strings. I can do this in the tapping tests very quickly, but as soon as I contact the strings, it's all "garage spikes". Appreciate any help you can give on next steps.