breeding help

I have a TAMUK buck that is 7 months old, two TAMUK does the same age, and another American Chinchilla doe that is 9 months old. They have a big beautiful 9x10 enclosure, with an external box with toys and two levels that is a 4x4x5 and an artificial Warren underground. Plenty of pellet food...

I have a new buck (5+ months) and he is willing but he hasn't fallen off when I tried breeding him. He is very interested in the doe and mounts but usually doesn't have things lined up. This is the first time trying to breed him since I got him around 3+ months old. I have put him with the same...