通常这个错误是由于导出的音频文件与原始音频文件有时间范围的重叠或不连续所造成的。要解决这个问题，需要在导出音频之前对原始音频进行修正或合并。以下是一个示例代码，演示如何使用AVMutableComposition和AVAssetExportSession合并两个音频文件：

let composition = AVMutableComposition()
let compositionTrack = composition.addMutableTrack(withMediaType: .audio, preferredTrackID: kCMPersistentTrackID_Invalid)

let asset1 = AVURLAsset(url: URL(string: "path/to/first/audio/file")!)
let track1 = asset1.tracks(withMediaType: .audio)[0]
let timeRange1 = CMTimeRangeMake(start: CMTime.zero, duration: asset1.duration)

let asset2 = AVURLAsset(url: URL(string: "path/to/second/audio/file")!)
let track2 = asset2.tracks(withMediaType: .audio)[0]
let timeRange2 = CMTimeRangeMake(start: CMTime.zero, duration: asset2.duration)

do {
    try compositionTrack?.insertTimeRange(timeRange1, of: track1, at: CMTime.zero)
    try compositionTrack?.insertTimeRange(timeRange2, of: track2, at: asset1.duration)
} catch {
    print("Failed to insert audio tracks into composition")
}

let exportSession = AVAssetExportSession(asset: composition, presetName: AVAssetExportPresetAppleM4A)
exportSession?.outputFileType = .m4a
exportSession?.outputURL = URL(string: "path/to/output/file")!

exportSession?.exportAsynchronously {
    if exportSession?.status == .completed {
        print("Audio export successful!")
    } else {
        print("Audio export failed: \(exportSession?.error?.localizedDescription ?? "")")
    }
}

在这个示例中，我们创建了一个AVMutableComposition，并将两个音频文件的音轨插入到组合中。第一个音频文件从0秒开始播放，第二个音频文件从第一个音频文件