verifyReceipt returns tons of errors 21104 and 21107

Hi, Sometimes I get tons of errors 21104 and 21107 in a row when I try to validate new subscriptions and renew existing subscriptions from our server side by using the endpoint verifyReceipt:

Code Block 
POST https://buy.itunes.apple.com/verifyReceipt

https://developer.apple.com/documentation/appstorereceipts/verifyreceipt

The response of this endpoint doesn't give any extra information:

Code Block 
{
    "environment": "Production",
    "status": 21107,
    "is_retryable": true
}

I noticed that those subscriptions are renewed on the second try after waiting a bit (in a different hour/day).

The documentation only indicates that the status codes 21100-21199 are internal data access errors but it doesn't specify each one:

https://developer.apple.com/documentation/appstorereceipts/status

I understand that it's an error on the Apple side so there is nothing I can do but if someone could give us more information about those errors (21104 and 21107).