Cannot read properties of undefined on formatter, but data is showing fine - vue.js

Question

I have a bootstrap table that shows a list of appliances. I am importing my data with Axios and for this specific table I am outputting data from two database tables, so I have one object which is called applianceReferences which stores another object called activeAppliances.
Not sure if it is relevant for this question, but just so you know.
Before talking about the problem, let me just post the whole code and below I will talk about the section that is giving me issues.
<template>
<b-container class="my-2">
<b-card v-if="showTable" class="ml-4 mr-4">
<b-table
search-placeholder="search"
:filter-included-fields="fields.map(f => f.key)"
include-filter
:items="applianceReferences"
:fields="fields"
/>
</b-card>
</b-container>
</template>
<script>
import {applianceService} from "#/services/appliance";
import CommonCollapsible from "#/components/common/CommonCollapsible";
import moment from 'moment';
export default {
components: { CommonCollapsible, CommonTable },
props: {
ownerId: String,
ownerType: String,
showDocuments: Boolean,
goToAppliances: "",
importAppliances: ""
},
data() {
return {
applianceReferences: [],
showTable: true
}
},
computed: {
fields() {
return [
{
key: 'referenceName',
label: this.$t('referenceName'),
sortable: true
},
{
key: 'activeAppliance.type',
label: this.$t('type'),
sortable: true,
},
{
key: 'activeAppliance.brandName',
label: this.$t('brand'),
sortable: true
},
{
key: 'activeAppliance.purchaseDate',
label: this.$t('purchaseDate'),
sortable: true,
template: {type: 'date', format: 'L'}
},
{
key: 'activeAppliance.warrantyDuration',
label: this.$t('warrantyDuration'),
sortable: true,
formatter: (warrantyDuration, applianceId, appliance) =>
this.$n(warrantyDuration) + ' ' +
this.$t(appliance.activeAppliance.warrantyDurationType ?
`model.appliance.warrantyDurationTypes.${appliance.activeAppliance.warrantyDurationType}` :
''
).toLocaleLowerCase(this.$i18n.locale),
sortByFormatted: (warrantyDuration, applianceId, appliance) =>
appliance.activeAppliance.warrantyDurationType === 'YEARS' ? warrantyDuration * 12 : warrantyDuration
},
{
key: 'activeAppliance.purchaseAmount',
label: this.$t('amount'),
sortable: true,
template: {
type: 'number', format: {minimumFractionDigits: '2', maximumFractionDigits: '2'},
foot: sum
}
},
{
key: 'actions',
template: {
type: 'actions',
head: [
{
text: 'overviewOfAppliances',
icon: 'fas fa-fw fa-arrow-right',
action: this.createAppliance
},
{
icon: 'fas fa-fw fa-file-excel',
action: this.importAppliance,
tooltip: this.$t('importAppliances'),
}
],
cell: [
{
icon: 'fa-trash',
variant: 'outline-danger',
action: this.remove
},
]
}
}
]
},
},
methods: {
load() {
Object.assign(this.$data, this.$options.data.apply(this));
this.applianceReferences = null;
applianceService.listApplianceReferences(this.ownerId).then(({data: applianceReferences}) => {
this.applianceReferences = applianceReferences;
this.applianceReferences.forEach( reference => {
applianceService.listAppliances(reference.id).then(result => {
this.$set(reference, 'appliances', result.data);
this.$set(reference, 'activeAppliance', result.data.find(appliance => appliance.active))
this.loaded = true
})
})
}).catch(error => {
console.error(error);
})
},
createAppliance(){
this.goToAppliances()
},
importAppliance(){
this.importAppliances()
},
},
watch: {
ownerId: {
immediate: true,
handler: 'load'
}
},
}
</script>
Okay, so the error occurs in this specific property:
{
key: 'activeAppliance.warrantyDuration',
label: this.$t('warrantyDuration'),
sortable: true,
formatter: (warrantyDuration, applianceId, appliance) =>
this.$n(warrantyDuration) + ' ' +
this.$t(appliance.activeAppliance.warrantyDurationType ?
`model.appliance.warrantyDurationTypes.${appliance.activeAppliance.warrantyDurationType}` :
''
).toLocaleLowerCase(this.$i18n.locale),
sortByFormatted: (warrantyDuration, applianceId, appliance) =>
appliance.activeAppliance.warrantyDurationType === 'YEARS' ? warrantyDuration * 12 : warrantyDuration
},
What I am basically doing here is combining two values from the object: warrantyDuration and warrantyDurationType and putting them in one single row in my bootstrap table.
The problem is that this is giving me an error: Cannot read properties of undefined (reading 'warrantyDurationType'
Yet the data actually outputs normally.
So what exactly does it want me to do?
I tried wrapping a v-if around the table to make sure that the application checks if the data exist before outputting it, but this does not solve the issue.
<div v-if="applianceReferences && applianceReferences.activeAppliance">
<b-card v-if="showTable" class="ml-4 mr-4">
<common-table
search-placeholder="search"
:filter-included-fields="fields.map(f => f.key)"
include-filter
:items="applianceReferences"
:fields="fields"
/>
</b-card>
</div>
Last, just to give you a full overview, my array looks like this:
Any ideas?