I have a GPO setup that sets up printers and sets up the default printer.
By accident, I forgot to add one printer (SupervisorPod). Upon doing so, I did notice the correct printer was set as default.
I then added the missing printer(SupervisorPod), and noticed it took the default printer setting, even though the GPO doesn't specify it as so.
I've taken a screenshot of the GPO in question.
For whatever reason, the "MC-SupervisorPod-BW" is becoming the default printer, if I remove it, the "MC-Dispatch-BW" printer becomes default. If it makes any difference, the Supervisor printer is using the HP Universal PCL-6 driver.