Why do Material UI CheckBox appear twice on the first render?

A weird thing is happening with my checkboxes and I can't figure it out. The first time the component loads, each checkbox appears twice. 2nd and subsequent loads are OK. Here is my code:-

const ModifierGroups = () => {
        return (
            modifierGroups.map(modifierGroup => (
                <div>
                    <FormControlLabel
                        className={classes.checkBoxes}
                        label={modifierGroup.Name}
                        control={
                            <MUICheckbox
                                checked={true}
                                name={modifierGroup.Name}
                                size="small" />
                        }
                />
                </div>
            ))
        )
    }

and this is what it looks like the first time it loads