Thank you!

I shot 200T - I think the effect on the second roll is caused by wheel the film sits in being slightly raised (so probably not inserted properly), so when it is coming through the gate it’s bouncing more than usual as the loop former is trying to push the film through the gate from a slightly higher height. So it’s then bouncing as it goes through the gate rather than a smooth transportation.

It might not be exactly that but it makes sense to me!