I hat the same Problem with Firefox printing with my Brother HL-5270DN so I now tried the driver Brother HL-5170DN - CUPS+Gutenprint v5.2.10-pre2 an not any other for Brother HL-5270DN, and that seems to work.
I hat the same Problem with Firefox printing with my Brother HL-5270DN so I now tried the driver Brother HL-5170DN - CUPS+Gutenprint v5.2.10-pre2 an not any other for Brother HL-5270DN, and that seems to work.