[Vuejs]-VueJS – Computed property has no setter (but actually has)

Instead of trying to make it work like you are by using references to other things, try to refactor your logic. Maybe you don’t need a v-model in this instance (which should be used with a variable defined in data() or directly with a getter / setting computed properties) but rather want to use a method bound to @input.

For components that use custom events and values for binding to v-model:
https://v2.vuejs.org/v2/guide/components-custom-events.html#Customizing-Component-v-model

For watching data and reacting to model changes:
https://it.vuejs.org/v2/guide/computed.html#Watchers