I had this same issue last year when my Plane Power died and I replaced it with a B&C - my initial run tests and flight tests, and all the troubleshooting followed yours exactly. Eventually I ended up at the hangar with one of their guys on my phone, and I ran through all his troubleshooting requests with a multimeter with no joy. He said "Send back the regulator and we'll send you a warranty replacement."
I sent it in, they cross-shipped one to me, and I asked them to please let me know if the regulator bench-checked out OK - so that I would know for sure the problem was on my end. I never heard back from them, and the replacement regulator worked perfectly.
Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2021 dues paid
N16GN flying 750 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, IFD440
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.