Vuejs doesn't update the DOM on Vuex mutation - vue.js

Question

I use Vue3 with Quasar2 and I have a problem during mutation: the DOM isn't updated.
The code consists of a parent component, a list of child components (rendered by v-for). The data comes from a Vuex store via computed property.
The child components only represent data and emit an 'edit' event with the id of the represented data.
On the 'edit' event the parent component fills properties with the actual data a presents a dialog.
When the dialog closes the parent calls an action to store the data.
The action (and the following mutation) are executed normally. The Vuex store contains the correct data.
But the list isn't updated :(
If I add a new element to the data list (via push) then the list will be updated.
Cleared sources are the following:
Parent.vue:
<template>
<q-page class="flex flex-center" :key="mykey">
<q-list padding>
<child-component
v-for="d in data"
v-bind:key="d.id"
v-bind:data="data"
v-on:edit-time="onEdit"
>
</program>
</q-list>
<!-- EDITOR DIALOG -->
<q-dialog v-model="editing" #hide="onEditDone">
....
</q-dialog>
<script>
....
export default defineComponent({
name: "PageIndex",
created: function () {
this.loadData();
},
data: function () {
return {
editing: false,
....
},
};
},
components: { Child },
methods: {
...mapActions(["loadData", "updateData"]),
onEdit(id) {
...
this.editing = true; // <= show dialog
},
onEditDone() {
try {
...
this.updateData(data); // <== Vuex Action which updates an elem of the data list
} catch (e) {
...
}
},
},
computed: {
...mapState({
data: state => state.data
}),
}
});
</script>
state.js:
export default {
data: [],
}
getters.js:
const getters = {
data: (state) => {
return state.data;
},
};
export default getters;
mutations.js:
updateData: (state, data) => {
var idx = state.data.findIndex((element) => element.id == data.id);
state.data.splice(idx, 1, data);
},
actions.js:
async updateData(context, data) {
try {
await axios.post(`api/data?id=${data.id}`, data, {
headers: {
"Content-Type": "application/json",
},
});
context.commit("updateData", data)
} catch (err) {
console.log(err);
}
},