PDT missing variables

[ionu]

Hi, I have an issue with PDT.

after payment, when the page returns to the merchant, from paypal, I do the request with the pdt token to get the info on the transaction.

Normally I get these parameters from paypal, in the case of a recurring sale:

                    [transaction_subject] => paypal product
                    [payment_date] => 19:53:02 Jul 12, 2018 PDT
                    [txn_type] => subscr_payment
                    [subscr_id] => I-XXXXXX
                    [last_name] => test
                    [residence_country] => CO
                    [item_name] => paypal product
                    [payment_gross] => 25.00
                    [mc_currency] => USD
                    [business] => vendor_email
                    [payment_type] => instant
                    [protection_eligibility] => Ineligible
                    [payer_status] => unverified
                    [payer_email] => buyer_email
                    [txn_id] => XXXXXXXXXXX
                    [receiver_email] => vendor_email
                    [first_name] => test
                    [payer_id] => XXXXXXXX
                    [receiver_id] => XXXXXXXX
                    [contact_phone] => 55555555
                    [item_number] => 1234
                    [payment_status] => Completed
                    [payment_fee] => 1.64
                    [mc_fee] => 1.64
                    [mc_gross] => 25.00
                    [custom] => 4321
                    [charset] => windows-1252
                    [] => 

but in some of the transactions the response from paypal lacks these 4 items:

subscr_id
item_name
item_number
custom

Any idea why they are missing? the purchases are identical, the only thing different is the buyer.

Thanks