Just an issue we have been noticing recently. Occasionally, we will have GS7 tell us that one or more of our listings has failed to upload (out of a group of 20ish). It does not show an error message like other failed-to-upload listings, but there is no checkmark next to the title like all the others after they upload, and it shows that X number of auctions failed at the bottom of the little pop up window.
When we look in eBay, we see that the auction DID upload, contrary to what GS7 shows. We actually put them through again the first time this happened and they uploaded fine... Thankfully, we realized the issue before one of the duplicated listing received a bid, and we were able to end the duplicates. We now check our active listings after the GS upload just to be sure none have duplicated.
We are running GS 7.0.6b7(790) on iMac version 10.12.3 (Sierra).
We experienced the issue described as recently as yesterday, and a few times before that since updating to GS 7 at the end of December.
Hopefully this is something that you are aware of and working on. Please let me know if you need any other info from us.