V-model value not updating in child component

Hi All, Im trying to wrap my head around what is happening and why. I am passing an object to my child component using v-model and I am a bit confused what is happening in the child component. My super simplified code is

<template>
    <div>
        <div 
            v-for="material in value.packaging"
            :key="material.SKU">
            <input v-model="material.pivot.unit" >

            {{ material.pivot.unit }}
        </div>
    </div>
</template>

<script>
    export default {

        props: ['value'],

        data() {
            return {
                // isPackaging: this.value.packaging,
            }
        },

    }
</script>

If I try to adjust the material.pivot.unit without uncommenting isPackaging the value doesn't update in the model. However, if I uncomment out isPackaging then it does update in the model even though I am not using isPackaging anywhere in my actual template code.