Google API revoked grants in unverified app - google-api

Question

Our app uses several different Google APIs. The app requests offline access for Google Search Console And Google Analytics.
Every now and then the grants given by users are revoked. Several users' grants are revoked, not at the same time, but in a timespan of a couple of days.
I've checked all the usual suspects, but nothing matches. Take my own account for example. I hadn't logged in for a week but all of a sudden my grants had been revoked. I verified that they were revoked in my Google account. So after a week of working, making offline requests, all the grants were revoked, except the basic one.
I'm using the Google php api package, Attaching the access token object to every request.
$this->client = new \Google_Client();
$this->client->setAuthConfig(env("GOOGLE_CLIENT_SECRET_JSON_PATH"));
$this->analyticsService = new \Google_Service_Analytics($this->client);
$this->client->setAccessToken($user->google_access_token_object);
I'm also also setting a callback for the request.
$client->setTokenCallback(function($cacheKey, $accessToken) use ($user, $client) {
$cacheEntry = $client->getCache()->getItem($cacheKey)->get();
$googleAccessTokenObject = json_decode($user->google_access_token_object, true);
$googleAccessTokenObject["access_token"] = $cacheEntry["access_token"];
$googleAccessTokenObject["expires_in"] = $cacheEntry["expires_in"];
$googleAccessTokenObject["scope"] = $cacheEntry["scope"];
$googleAccessTokenObject["token_type"] = $cacheEntry["token_type"];
$googleAccessTokenObject["id_token"] = $cacheEntry["id_token"];
$googleAccessTokenObject["created"] = time();
if(!empty($cacheEntry["refresh_token"])) {
$googleAccessTokenObject["refresh_token"] = $cacheEntry["refresh_token"];
}
$user->google_access_token_object = json_encode($googleAccessTokenObject);
$user->save();
});
This works without problems for weeks, but then it's like Google decides to revoke every extra grant given to the application.
None of the points brought up in this article are valid for us:
https://blog.timekit.io/google-oauth-invalid-grant-nightmare-and-how-to-fix-it-9f4efaf1da35
Since more than one account is affected during a timespan of a couple of days (this has happened multiple times) it doesn't seem to be an account based issue, but rather an application level issue.
The app in Google developer console has the "Publishing status" set to testing. I haven't found any info claiming that would be an issue though.

Answer 1

There are serval reasons why a refresh token will expire. The most common one these days is
A Google Cloud Platform project with an OAuth consent screen configured for an external user type and a publishing status of "Testing" is issued a refresh token expiring in 7 days.
Actually they have the consent revoked after seven days which basically causes all refresh tokens to expire.  
So the solution is to set your project to production, No this does not mean you need to verify it that is a separate setting.
Once your project is set to production you refresh tokens will stop expiring.