I have had this issue in the past, and it seemed to be completely at random. I have had at various times the Shipping Policy & Return Policy getting dropped on an automatic relisting, usually on auctions.
This week it seems to have happened on 60 +/- of my auction listings that had the "relist automatically up to 8 times" checkbox checked. I had an issue with it showing "Free Shipping" to a bidder, and when he went to pay it had a shipping charge that he had to pay. I went in and checked the listings, as they have automatically relisted and sure enough the Shipping Policy & Return Policy was missing, again.
I checked the listings while not signed into an account, and on a computer it calculated the shipping correctly, but on the mobile app it said local pickup only. I also found that on the mobile app several of my fixed price listings the shipping is sometimes listed as "+shipping" in the list, but when you go into the item, it says free shipping (free shipping was being offered on those items).
This could get worse as the new listing tool is rolled out, as when I tested it today, I found that Package Size, Shipping Policy & Return Policy sometimes goes missing when I go to edit an item, just like to does on the mobile app.
