had a Makita DHP456 brought to me, the guy said it was smoking changed motor and brushes and sent it back 3 days later he returned it and said it was still smoking.
looked at it again 100% tested not smoking at all i finally worked it out.
the guy was cutting holes in the seiling for sunken lights, he was holding drill by handle and also putting hand over the base pushing upwards (WRONG).
do not not put your left hand on the bottom and push up, simply hold by handle and push up slowly let the cutter do the work if it doesn't it maybe blunt (buy a new cutter).
holding in right hand then using left hand to push up you block the air vents causing overheating of the motor and hence it smokes,

hope this helps