hello, I'm using mach 3 breakout board with TB6600 stepper controllers and i use fusion 360 to build my models

all the cuts i make they are losing 0.5mm like if i cut a 15x15mm square it will be 14.5x14.5mm and if i make a pocket it is creating a weird slope at one side
check in the attachments and same way losing 0.5mm

i have pretty much checked everything on the machine and software but cannot fix this issue