Since top rated sellers in the U.S. obtain shipping discounts for labels printed for USPS services this can to instances where shipping via the faster Priority Mail is actually cheaper than shipping the slower Parcel Select since I often obtain discounts of 35% for Priority Mail. This comparison of costs is determined by the destination zip code and by the fact that Priority Mail includes $100 of free insurance whereas Parcel Select does not.
I have no way of knowing the customer’s zip code beforehand so I typically list items with both shipping services - “USPS Parcel Select” and “USPS Priority Mail”. For certain listings I also use free shipping by checking the small checkbox.
When the listing appears on eBay only the service that appears next to the checkbox appears as free while the second (and third service) chosen in GS will be shown at it calculated price. This is not what I want to be shown. What I want to indicate to customers is that I will be include free shipping and ship the item for free via the cheapest service, which could either be Priority Mail or Parcel Select (or via Media Mail in the case of books).
Each service needs its own “Free” checkbox or the single “Free” checkbox should apply to all the services shown. Not sure if you can fix this as it could be an issue with how eBay’s API works, but perhaps you can talk to them to get it changed if that is the case.