Calling engine.start() redirects stdout/stderr; can't see my own print statements

[fyh333]

After I call engine.start(), it seems like the standard input/output is redirected. I can no longer see my own print statements in the console. How can I fix this or work around it?

[fyh333]

The other problem:
I'm encountering a crash when I call the submitFENToEngine(fen:) method, but Xcode doesn't show any stack trace or useful error message. Here's a simplified version of my code:

import Foundation
import ChessKitEngine

class UCIEngine {
    let engine = Engine(type: .stockfish)
    
    var foundBestMove: (_ from: BoardIndex, _ to: BoardIndex) -> Void
    
    init(foundBestMove: @escaping ((_ from: BoardIndex, _ to: BoardIndex) -> Void)) {
        self.foundBestMove = foundBestMove
        
        engine.start(coreCount: 2) {
            
        }
        
        engine.receiveResponse = { response in
            switch response {
                case .bestmove(let move, let ponder):
                    print(move, ponder ?? "")
                    if let bordIndexMove = self.convertUCIMoveToBoardIndex(uciMove: move) {
                        foundBestMove(bordIndexMove.0, bordIndexMove.1)
                    }
                default:
                    print(response)
                    break
            }
        }
    }
    
    func submitFENToEngine(fen: String) {
        engine.send(command: .stop)
        engine.send(command: .position(.fen(fen)))
        engine.send(command: .go(depth: 10))
    }
    
    private func convertUCIMoveToBoardIndex(uciMove: String) -> (BoardIndex, BoardIndex)? {
        guard uciMove.count >= 4 else { return nil }
        
        let uciMove = uciMove.prefix(4)
        
        let originPosition = uciMove.prefix(2)
        let targetPosition = uciMove.suffix(2)
        
        guard let originIndex = BoardIndex.fromString(indexString: String(originPosition)) else { return nil }
        guard let targetIndex = BoardIndex.fromString(indexString: String(targetPosition)) else { return nil }
        
        return (originIndex, targetIndex)
    }
}

Do you have any idea what might be causing this issue?
Also, why doesn't Xcode show a stack trace in this case? Is there a way I can debug it more effectively?

Thanks in advance!