There is just no "one size fits all" answer here.
The typical cash plus boot transaction will not allow a loss and if that was the case here then the basis in the new stock would be $42,000 - $10,000 cash + $0 gain = $32,000. And this latest sale would be $33,000 - $32,000 = $1,000.
But if the broker is really reporting the basis as $28,000 that suggests that this was one of those deals where gain (and probably loss) could be recognized based on the total proceeds - cash plus stock - of $38,000 and $38,000 - $42,000 = ($4,000). The basis of the new stock actually would be $28,000 as reported by the broker so $33,000 - $28,000 = $5,000.
The original reporting might have been incorrect.
