Error in audio recording WAV - wav

Question

I have two methods that record audio every 10 minutes, alternating each method, properly recorded during the first 6 or 7 hours, but then I generates large files to twice normal to hear hear bad but only happens with a method other Normal still recording. I use to record WaveInEnvent since the method is inside a thread, I think problem is in OnDataAvailable.
Here the code used:
wavein = new WaveInEvent();
wavein.Dispose();
wavein.DeviceNumber = 0;
wavein.NumberOfBuffers = 11;
wavein.BufferMilliseconds = 1000;
wavein.WaveFormat = new WaveFormat(8000, 16, 2);
wavein.DataAvailable += OnDataAvailable;
wavein.RecordingStopped += OnRecordingStopped;
writer = new WaveFileWriter(outfilename, wavein.WaveFormat);
bufferedWaveProvider = new BufferedWaveProvider(wavein.WaveFormat);
bufferedWaveProvider.DiscardOnBufferOverflow = true;
wavein.StartRecording();
private void OnDataAvailable(object sender, WaveInEventArgs e)
{
if (this.InvokeRequired)
{
//Debug.WriteLine("Data Available");
this.BeginInvoke(new EventHandler<WaveInEventArgs>(OnDataAvailable), sender, e);
}
else
{
if (writer != null)
{
try
{
for (int i = 0; i < e.BytesRecorded; i += 2)
{
short sample = (short)((e.Buffer[i + 1] << 8) | e.Buffer[i + 0]);
float sample32 = sample / 32768f;
writer.WriteByte(e.Buffer[i + 0]);
writer.WriteByte(e.Buffer[i + 1]);
}
}
catch (Exception ex)
{
// Log error
}
}
}
}