I'm going to throw out a couple of guesses.

For your first problem, try seating the bullet a bit deeper. Sounds like you are contacting the lands and grooves.

If new brass chambers, it doesn't sound like a headspace or chamber issue.

I'd call cooper and ask how long their throat is cut, and go from there.

That sucks! Good luck getting it worked out. I'm sure they will bend over backwards for you.