There is a log of the request. If you go to your logs you should see the request and who/what app made it. For example:
{
"date": "2021-08-11T19:05:55.349Z",
"type": "sapi",
"description": "Update a User",
"client_id": "xxxxx",
"client_name": "xxxxx",
"details": {
"request": {
"method": "patch",
"path": "/api/v2/users/xxxxx",
"query": {},
"body": {
"app_metadata": {
"foo": "bar"
}
},
"channel": "https://manage.auth0.com/",
"auth": {
"user": {
"user_id": "xxxxx",
"name": "xxxxx",
"email": "xxxxx"
}
}
//...etc...
}
You can also search the logs, which should help you narrow down the requests that are clearing the app metadata.