So awhile ago I posted about pre-filling an embedded form on an external landing page based on Marketo's unique code. The concept and solution we went with after some input on here was we mail/email the unique code to a customer, they just enter that code into a custom html form on our external landing page, it passes that unique code to a Marketo landing page and grabs their info of our choosing, then redirects them back to a second external landing page with an embedded Marketo form and prefills it with their data. So basically the user just sees they enter a code then get brought to a second page with their info prefilled on an embedded form.
This was working fine but now we're running another similar campaign and when trying to test this out on the new landing pages the embedded form isnt being prefilled with the data associated with the unique code. So I started logging the unique code Marketo is pulling and the object with their data to try and troubleshoot and I can see the known unique code we enter into the form isn't the one the Marketo page tries to use. Also, each time I test the same code, the one Marketo tries to use is different than the previous one assigned to me. This testing is being done in incognito tabs to prevent complications associated with Marketo cookies.
Based on this behavior it appears that once we hit the Marketo landing page it is assigning a unique code to the anonymous visitor and ignoring the unique code they entered (which is just appended to the end of the URL of the landing page with personalized URLs enabled).
So for example the person enters ABC123 and it redirects them to: xyz.com/lp/ABC123 but in the browser console I can see it is using Marketo code DEF456. Then I close out and re-enter ABC123 into the form and the console shows GHI789 when on the Marketo page.
1) Is that the correct assumption about Marketo's behavior assigning a unique code to an anonymous visitor before they even submit a Marketo form?
2) Is this behavior something we can correct? Disabling munchkin tracking didn't help.