They'll probably say it wasn't broken in yet about the out of spec BCG. Just put 1000 rounds through it, and the upper would have cycled better.
I'd think a BCG and drill out the gas port to the next size would do it for you.As much as I hate to turn people off a company due to one bad product, given the failure of customer service, I don't think I could recommend Springfield to anyone. They've certainly lost a customer permanently in me. Just contrasting this experience with PSA, a cut-rate, although decent quality gun maker, it's night and day.
I reevaluated the flash hider today, and I'm less sure about the severity of that problem. Internal damage to the upper receiver due to gouging from the Sharp BCG is not extensive. I'm more optimistic I can ultimately save the upper receiver, replace the barrel, swap the gas tube/block, drop in a FZ BCG, and maybe have a functioning gun.