X5 doesn't stay stopped

[Buxexanic]

Hey guys! I'm having problems diagnosing some brake issues. The car decelerates like normal and the pedal feels relatively normal. Once I'm stopped, the car doesn't wanna stay stopped, I have to keep a lot of pressure on the pedal. The pedal does not become mushy and its not throwing any codes for the brakes.

I replaced the front pads first as they were already pretty shot. Didn't help
I flushed the brake system hoping it was an air bubble. Didn't help

I'm thinking the next step is to replace the master cylinder, but I'm a little apprehensive to do so since I don't have any codes for it and I don't lose pedal pressure.

Other ideas: Bad DSC unit, bad brake booster, rotors too smooth? Is this too out there?

Anyways, if anyone has had a similar problem or has some info for me it would be greatly appreciated.

Thanks in advance!