This is the true diagnostic. Microsoft’s RDP stack defines 0x12 as a failure in either:
The Remote Desktop error code 0x3 and extended error code 0x12 typically occur when a user tries to connect to a remote computer using Remote Desktop Connection (RDC). The error message may appear as "The remote computer disconnected. The error code is 0x3 and the extended error code is 0x12." remote desktop error code 0x3 extended error code 0x12
w32tm /resync
CredSSP is a security protocol that provides a secure way for clients to authenticate with servers. It's used in Remote Desktop connections to validate the user's credentials. This is the true diagnostic