Azure AKS and Application Gateway returning 404 - azure

Question

I have a AKS cluster deployed with an Application Gateway. These are all docker images running on the AKS cluster with a simple ingress. They all run on the same default namespace. One is a Vue frontend, the second is a Java spring backend, the last being a Fullstack Tomcat image. All three services ran completely fine without any issues; however, today all of the 3 services gave back a 404 error (without any changes to the cluster to my knowledge).
When testing for the health of these services, I was still able to kubectl to all the services. In addition, the Health Probe on Azure Application Gateway returned a healthy 200 status code for all three services.
I have tried removing the workloads and adding them back again. I have tried removing the services then adding them back again. I have done the same for the ingress as well.
I have also tried setting up the entire cluster from a fresh AKS cluster from scratch from a new AKS cluster, all three images perform without any issues.
The Yaml for a application on the AKS network looks like:
- apiVersion: apps/v1
kind: Deployment
metadata:
name: testvuefe
spec:
replicas: 2
selector:
matchLabels:
app: testvuefe
template:
metadata:
labels:
app: testvuefe
spec:
nodeSelector:
kubernetes.io/os: linux
containers:
- name: testvuefe
image: testdocker.azurecr.io/testvuefe:latest
ports:
- containerPort: 80
resources:
requests:
cpu: '0'
memory: '0'
limits:
cpu: '128'
memory: 512G
volumeMounts:
- mountPath: "/fileShare"
name: volume
volumes:
- name: volume
persistentVolumeClaim:
claimName: aks-azurefile
- apiVersion: v1
kind: Service
metadata:
name: testvuefe-service
spec:
type: ClusterIP
ports:
- targetPort: 80
name: port80
port: 80
protocol: TCP
selector:
app: testvuefe
- apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
name: testvuefe-ingress
annotations:
kubernetes.io/ingress.class: azure/application-gateway
appgw.ingress.kubernetes.io/health-probe-path: /user
appgw.ingress.kubernetes.io/cookie-based-affinity: "true"
spec:
rules:
- host: test.wbsoft.co.kr
http:
paths:
- path: /
pathType: Prefix
backend:
service:
name: testvuefe-service
port:
number: 80
As this issue as occurred once on a cluster, I need to understand what is causing these issues so that it does not happen during production. It would also be great if a solution can be found for the issue.