MacBook Pro 2016 locks upon boot, password not recognized

This is very odd, and no consultant I know of has ever seen this outside of an enterprise situation. New MBP 2016 appears to lock itself into FileVault by default, yet not recognize the password, even after reset with AppleCare. Second time just wiped the SSD and reinstalled fresh from Recovery (Internet). Worked for fine for about an hour and again next day. Then after that it appears to have locked itself again with same problem. Password was local not using the Apple ID the last time, and set-up was done off-line. macOS version used is Sierra.