Getting the data back from child to parent element in Vue - vue.js

Question

Before last updates I used a custom component to work with sliders. Works perfectly, but after upgrading I got a problem.
This is the wayI use my custom component:
<ta-slider2 v-model="stelling1"/>
This passes the value to the custom component and received the data back.
This is my custom component
<template>
<div class="mt-3">
<div><br><br></div>
<v-slider
prop="value"
v-model="interface"
:value="value"
:color="color"
always-dirty
min="-100"
max="100"
thumb-label="always"
>
<template v-slot:append>
<v-icon color="blue">add_circle_outline</v-icon>
</template>
<template v-slot:prepend>
<v-icon color="error">remove_circle_outline</v-icon>
</template>
</v-slider>
</div>
</template>
<script>
export default {
name: "ta-slider2",
props: {
value: null
},
data() {
return {
}
},
computed: {
interface: {
get() {
return this.value
},
set(val) {
this.$emit('input', val)
}
},
color() {
if (this.value < 0) return 'red'
if (this.value > 0) return 'blue'
return 'red'
},
},
}
</script>
<style scoped>
</style>
Worked perfect but now the line with v-model="interface" gives problems. Googled for hours but can not find a solution. Who can help me out?