Hi!
Welcome to BYC! Good luck with integrating your cockerel. All of your chickens are in their first year, so still pullets and a cockerel. It may be a question of immaturity.
But honestly, integration can be very difficult. When I do it, I sit out and watch that no one gets hurt. Sometimes it goes very smoothly, especially when it's pullets and hens. But integrating a cockerel brings with it a huge change in the flock.

Also, this. It might take a couple weeks of look don't touch intro before integration.Several days went by with very little attention toward either side.
But honestly, integration can be very difficult. When I do it, I sit out and watch that no one gets hurt. Sometimes it goes very smoothly, especially when it's pullets and hens. But integrating a cockerel brings with it a huge change in the flock.