You were asking the proper questions & original poster's replies do not appear
to have been detail oriented; as though the information stressed as important
was not seen or read as such...

...and also, other types of discs were tried before or after your answer included
the warning about BlueRay media as not being compatible with SuperDrives.
Also, if using various Region Code-sourced DVD retail movie media discs
at some point the few code options may be cycled through, so no DVDs
would be able to work at all once all of them are used up, as you know.
There may be a way to take-apart an Apple USB SuperDrive, if not under
warranty at Apple anymore, or at least replace an optical drive in the case.
{In the following page, there is a second link to the 'firmware patch' to make
these work (for some models) as an external superdrive to Macs whose
original built-in superdrive had failed.}
•Apple USB SuperDrive Repair guide - iFixit:
https://www.ifixit.com/Device/Apple_USB_SuperDrive
So as you've suggested, a visit to an Apple Store with Genius bar, with an
appointment set ahead of time could be the answer to several issues here.
Good luck & happy computing! 😐