I had the same issue. Taking help from TT expert didn't help much but on the review page, when you click the Fix button, you get the form 8949 on next page. On top of that page you see a text box for Adjustment of cost basis. Enter 0 in this box and continue. This will make your error disappear without making any change to your tax refund/due amount. You will also notice that your entries for the proceeds and cost basis remains as is as it was before entering 0. So I really don't know what it does internally, but lets the weird error disappear. I already spent 4 hrs to fix the issue. Don't want you to spend more time on this.
Good Luck!
Raj
