Remote Desktop Gateway behaviour change after 4 years. No longer prompted for second credentials when targeting a different internal domain joined machine.

Question

Hello all,

We had a solution what worked for years allowing certain users access to an internal second domain machines for admin work. This would hit the remote gateway and prompt for external domain credentials and then for 2 factor before passing through to second domain machine and then prompting for second domain credentials. Last week it started passing through the external domain credentials to the internal second domain giving an incorrect username password error on that machine. We are in a change freeze so no changes made. Anyone else have a similar solution or problem occur?