I have the same issue. I have 3 RSU transactions. 2 of them have Cost Basis accurately calculated. One doesn't.
The one with the error has 3 RSU's vested. 2 Sold for taxes. TurboTax calculates cost basis as if just one share sold. If I set the number of shares vested to 4 or higher. The calculation works as expected. But I don't know if that is a safe workaround.
I have spoken to multiple Intuit people. They can't explain it and do not care. Refund is the only option if you don't like it or can't figure out a workaround for their bug. Last time I'm using TurboTax. Have RSU issues like this every year and they never get fixed.
