[SOLVED} Cannot change printer defaults

[hmonster]

Hi, I have recently migrated to Mint 19 from Ubuntu 18.04. I have a Brother MFC-J4610DW printer. I have set it up using the Brother install utility downloaded from their website and it appears to print fine. My problem is that I cannot change any of the printer defaults either via the system-config-printer utility or via the CUPS browser interface.

When I try to change any options using system-config-printer utility, they revert to defaults directly I press the Apply button. I have tried running the dialogue from the terminal using sudo with the same result.
When trying to change via the CUPS browser interface I get an Unauthorized message, but no way of entering the root id/password.

I was able to change the defaults OK in Ubuntu 18.04 after installing the printer in the same way as I did on Mint 19.

Any ideas as to how I can change the printer defaults? It is annoying to have to override the paper size to A4 every time I want to print something out.

[hmonster]

OK, I am a bit confused now. I solved this problem by going into printer settings and re-selecting the same Brother printer driver again. When prompted, asked to copy old PPD settings over to the new driver. I can now edit the printer options, and when I press apply they do not get regressed back to the default.

Not sure why this should work but it seems to have done the trick.