I am sure those were running at 60 wpm which was the standard for
non-military teletypes in those days. Imagine them running at not quite
twice the speed. They sound like they are self-destructing.
Usually the thing that goes to hell in a hurry when you speed up an
impact printer is print quality. The type face (drum, ball, typebar or
whatever) doesn't get time to properly align and the characters jump
around on the page.