@datastream This might be a case that requires using sysprep if you aren’t already. I had to learn all about going into audit mode and using the unattend.xml file for prepping the first golden image for our district when we were forced to start rolling out Windows 10 before we were ready (thanks Intel for not supporting Win 7 updates on newer chipsets…).
Anyhow, I do the entire setup in audit mode with the built in administrator account. When the OOBE runs my unattend file injects the activation key, re-enables the local admin account, sets the password, auto-logs in for some scripts to run and other fun stuff before I have the FOG client service turn back on via the systemcomplete.cmd file so that FOG can set the PC name and join the domain. Never had any issues with passwords.
Out of curiosity, which build of Windows 10 are you trying to deploy? With how wonky Windows 10 has been there may be some additional setup required to meet your needs.