Update HubSpot Property Based on User Landing Page Sign-Up

Objective: Update the HubSpot contact property "Where did you hear about us?" based on the specific landing page where a user signed up. Context: I have several unique landing pages (e.g., `shiftgroup.io/{{unique_subpage}}`). My goal is to identify which users signed up from each specific landing page and update their contact properties accordingly. Current Setup: For example, John Doe visited this landing page: `https://shiftgroup.io/linkedin-recruiter-new-candidate/` and created an account. Mixpanel logs this as an "Account Created" event. To gather this data, I’m using the Mixpanel API (`https://data.mixpanel.com/api/2.0/export`) to pull "Account Created" events from the past 24 hours. I've written a script that filters by referral URL so I can assign the correct HubSpot contact property based on the user's original landing page. Issue: While the API call and script work partially (some users show the expected referral URLs), **not all users** from these landing pages are captured, even if they created accounts. Problem: The "Account Created" event doesn’t consistently include the URL of the landing page where users signed up. Interestingly, the "Viewed" event in Mixpanel does show a referral property (e.g., "linkedin-recruiter-new-candidate/"), which could help—but this property is missing or inconsistent in the "Account Created" event data. Any help is much appreciated!!