Yes the conflict in GS also arises from some other Category requirements getting “out of sync”. In my case, it’s usually “Condition”.
The Condition is set and active in the listings. The problem is that the Categories data from eBay somehow gets corrupted or deranged (almost certainly from the server side), and a given item’s Category is changed so that on my local GS verifier that category doesn’t say it needs Condition, when eBay still believes it does. So the GarageSale (which has incorrect requirements) will locally say a listing is fine, but eBay (which has probably? not updated those requirements) will say it needs Condition.
This seems to happen spontaneously every few weeks.
If there is a GS bug, it is somewhere in the code that updates the required Attributes for categories, or which removes non-required Attributes from uploads. For whatever reason, the GS requirements list becomes incorrect, compared to eBay’s server-side verification list.
The behavior I would expect is: If I set Condition (or Best Offer, or any of the other things) to a non-null value in a listing, I would expect GS to attempt to upload that field, whether it is required or not. At the moment, if I have the field set locally, and GS imagines that it is not required, it does not even try, and the server complains that it is required.