Op here...
Manufacture called me back today. He says they used brass because
1. Have less problems getting out compared to steel bolt, if they need to.
2. When they do get returns many times the owner states that they haven't taken it apart or messed with the entire unit. The soft brass tells a different story because it is so soft they can tell if owner has monkeyed with it or not (I guess wrench marks on the soft brass)
There sending new brass plugs and say torque on big hole is (1/2 inch) 30 psi. Smaller one 18 pounds.
Also said they have had about a dozen in about the last year with same problem. Problem not unheard of but not very common.
I'm going use that "Rocksett High Temp Adhesive" and torque to spec's and score one edge of new plug and check every now and then it hasn't moved.
Thanks for all the help.