Is the wheel eroded at the bead area? Mark the area and turn the tire on the rim. If the leak follows the tire the bead may be bad. Most of the time cleaning the rim and using bead sealant fixes them up.
X2 with this. Also, just throwing this out there-- my wife had tires put on her vehicle and one of them was always slowly leaking. After a few weeks, I pulled the wheel and dunked it. Found the leak point, deflated tire and peeled back bead. Saw the barcode sticker wasnt removed. After removing, gently scuffed wheel and bead with a fine scotch Brite pad and it sealed great.