当在调用broadcastPaused()函数后异步写入音视频时，可能会遇到此问题。解决方法是使用AVAssetWriter的waitForAsynchronousWrites()函数来等待异步写入完成，然后再调用finishWriting(completionHandler:)函数结束视频录制。

示例代码如下：

// 在调用broadcastPaused()后异步写入音视频
writer?.startSession(atSourceTime: CMClockGetTime(CMClockGetHostTimeClock()))
if writer?.status == .writing {
    let audioInput = audioWriterInput
    let videoInput = videoWriterInput
    
    // 异步写入音频和视频
    writer?.startWriting()
    writer?.startSession(atSourceTime: CMSampleBufferGetPresentationTimeStamp(sampleBuffer))
    if audioInput.isReadyForMoreMediaData && videoInput.isReadyForMoreMediaData {
        audioInput.append(sampleBuffer)
        if let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) {
            let timestamps = CMSampleBufferGetPresentationTimeStamp(sampleBuffer)
            videoInput.append(imageBuffer, withPresentationTime: timestamps)
        }
    }
    
    // 等待异步写入完成
    writer?.waitForAsynchronousWrites {
        writer?.finishWriting(completionHandler: { [weak self] in
            // 结束录制
        })
    }
}