In Google Analytics, I have about 32% of all transactions attributed to Direct traffic. However, direct traffic only drives about 15% of visits.

Even more puzzling, the ecommerce platform's own analytics attributes about 90% of transactions to direct traffic, and Hubspot does the same.

The tracking snippets are on all pages, but referrer data isn't getting passed along somewhere in the checkout process (I assume).

The website is http, then transitions to https for checkout. However, it's all the same domain. I know GA accounts for transitions like this, and surely Bigcommerce and Hubspot would do the same?

Any ideas on how to debug? Or solutions?