If managed to get through the tough Enhanced Ecommerce implementation, you might find the next heads-up very useful:
If you collect data from subdomains, let’s say m.yoursite.com and www.yoursite.com (an often approach for websites) certain data from Ecommerce reports in Google Analytics will not be accurate at all on an aggregated level.
Let’s say you want to report on Product Performance:
The data will be incorrect because of certain deduplication algorithms employed by Google Analytics, on the server side of things.
The only way to correctly report data is to report by filtering on the individual subdomains and to not report on the aggregates:
Or report the data from a filtered view for that subdomain.
The problem affects mostly product related metrics: list views, detail views, unique purchases, list positions, etc in Enhanced Ecommerce implementations.
How can you verify and avoid this?
Simple: make a report that has “Product” as a dimensions and a metric of your choosing. Then filter it on subdomains and check if the metrics add up.
Hope this helped.