Custom parameter not being sent with some IPN requests

[grazer]

I am using a custom param to link accounts to PayPal subscriptions. Recently some IPN notifications have been missing the "custom" parameter, causing them to fail and retry.  How can I troubleshoot these transactions to see where the parameter got dropped?  When testing payments, the param appears to get sent properly.

Thanks in advance.

[MTS_Ciaran]

Can you post a transaction ID and we can check if it's being sent across, also send over a link to where we can test the flow. 

[grazer]

Here's an example:

Transaction id: 55344643N8024684V

Message id: 5LV77165N7197621J

The payment screen for that transaction is here: https://flowlab.io/users/upgrade?plan=education

But it will only be visible if you sign up for an account: https://flowlab.io/register/sign_up

(valid email address is not required or validated here)

Thanks in advance for any info.

[MTS_Ciaran]

Thanks pal. 

So this is a subscription payment so the IPN wouldnt actually contain the original custom variable, the custom variable is only passed through for the original IPN message, for the transaction/signup that it was originally sent to us in.