I have integrated paypal in my Magento 2 store. In live mode the transaction was fine but in Sandbox mode the 90% of times I get this response in the payment/4564564/execute call:

2018-05-31T17:11:22+00:00 INFO (6): Magento\Framework\DataObject Object
(
    [_data:protected] => Array
        (
            [http_status] => 500
            [status] => 500
            [response_code] => -1
            [response_reason_code] => 0
            [message] => Unable to read response, or response is empty
        )

) 

Recently I got the same error on live mode and I don't know why. This sometimes happens, the purchase is charged but the order is not generated.

Someone can help me?