Most shops when they balance a tire will have the machine tell them where to put the weights. This also means it's only checking the balance by spinning it which essentially doesn't check for other tire/wheel issues.
The wheel/rim may be bent or the tire may have an irregularity, but these defects may not put a wheel out of balance, but still shake a tire (side to side instead of perpendicular to the axis).
What kind of shaking are you getting? Where do you feel it?
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