Hey folks, can anyone help me out?

I'm almost done assembling a CNC machine, but I've run into a single issue: the machining is offset by approximately +-0.5 mm.

When I mill a pocket, it leaves it 0.5 mm higher, and when I profile, it's 0.5 mm lower. Sometimes it gives me more or less measurement, but generally it's around +- 0.5 mm. Occasionally, it gives me the exact measuremen

I've meticulously calibrated the motors (using Mach3) and even manually input exact coordinates, as I'm using 1204 ball screws.

I'm starting to feel desperate here. I'm programming with Vectric Aspire, and it's strange because I don't have any issues with another machine using the same software. It feels like there's something I'm configuring incorrectly.

Any ideas, guys? Could it be that the board is defective? I´m using the red bitsensor board