F5 APM - Secure Flag Causes Post to fail

I'm using a client initiated form to post a variable to Epic healthcare application. I have my credential mapping setup and it correctly reflects my username and password which I will be posting to the Epic application. The SSO mapping is also setup to map the session username / password variable to session.sso.token.last.username / password. These fields all reflect the correct value (Validated through message boxes and checking session variables).

Variables (All correct values)

session.sso.token.last.username = session.logon.last.username
session.sso.token.last.password = session.logon.last.password (Both Secure)

When I post to the application, I get an bad password. The only way I can get it to work is to use mcget -secure and assign it to another variable ("New Variable"). Then map "New Variable" to my SSO credential field for password. If I assign the "new" variable with a secure variable (IE mcget { password } = "New Variable") and map it to SSO, it fails.

What does marking a variable as -secure do when it posts? And no, I can't get a dump of the server because that would make this too easy.

Code version 12.1