Need help, 67 Camaro with rhs 502

[sic7camaro]

When I go to start it, the starter seems to engage the flywheel and spin the motor a little and then a loud bang and it seems like the motor kicks back the opposite way.
Sometimes it will turn and fire up, but seems like it runs a little rough.

Here is a video I made of it. The first two starts are with the coil harness plugs disconnected and it spins the motor fine like that. The others are with them connected and you can see how the motor seems to kick back https://m.youtube.com/watch?v=gmSln5mdTEc