pro(re)gress

 Paypal PDT/IPN - HTTP status Error 302 happens when you are contacting paypal via http while (as far as I can understand) they have enforced the requests to be via SSL (443 https)  and not in simple http requests (80 http). It happens in sandbox and live.

The Paypal error 4003 (when receiving PDT) could happen the server is doing too many requests/validations for the same "tx" (transaction id) with a cmd=_notify-synch. Paypal will not send back the data after about 5 requests. Sometimes the error could happen randomly in sandbox. This shouldn't happen in "live".

merchant_return_link=click+here merchant_return_link=return+to+merchant merchant_return_link=* it could happen if: the client browser is clicking the button while not accepting/using/respecting the META tag redirection the autoreturn is set to off in the the merchant account an url rewriting could be a solution