FL 2 Brakes Non existent

2.2 diesel auto. Had a new master cylinder about 8 months ago. Pads are all good. BUT.
I have to keep bleeding a ton of air out every single week. I've checked the non return valve, can't find any leaks, all pads and calipers seem to be good but every week the fluid is just full of bubbles.

I'm baffled.

Are the brakes working correctly? Has the system ever been completely empty? If so then air can be trapped in the ABS modulator. Reverse pressure bleeding it should help get all the air out. Alternatively use a diagnostic device like the IID to activate the ABS pump so the system can be purged under pressure.