Current Sensor Layout
Each square of copper foil in a standard-thickness PCB-foil (1 ounce of copper per square foot) has resistance of 0.000498 ohms (0.5 milliOhms).

Your layout has about 50 squares of copper in the high-current paths. At 0.4 amps, that become 50*0.5 milliOHms = 25 millOhms, or 10 milliVolts. Or 4 milliWatts. Not a big deal all distributed like that.