Simple example only works correctly first time, Why? - events

Question

This is a simplified snippet of a larger WPF project to illustrate the problem.
When the play button is pressed, this code plays the mp3's "1, 2, 3, 4, 5" then stops.
When the play button is pressed, the dispatch timer starts. On every Tick, the Metronome_Run event is called. The Metronome_Run event assigns a mp3 to play by indexing an array.
The problem is, it works fine the first time you press play, you get 1,2,3,4,5, but when pressing play again, you get 2,4,5, then pressing play again, you get 3,5! As if the indexing of the files seems to be offset each time play is pressed somehow.
When stepping through with the debugger, it runs perfect every time, yet without any breakpoints set, (like in the build), it works correctly only the first time and does not work correctly on further play button presses.
Any help is appreciated!
public partial class MainWindow : Window
{
private MediaPlayer mediaPlayer = new MediaPlayer();
List<int> NoteValArray = new List<int>() { 1,2,3,4,5 };
private DispatcherTimer timer1;
int numVal = 0;
int numIndex = 0;
private float tempo = 35f;
public MainWindow()
{
InitializeComponent();
timer1 = new DispatcherTimer();
}
private void Metronome_Run(object sender, EventArgs e)
{
if (NoteValArray.Count > numIndex) // if we are not outside the list bounds
{
numVal = NoteValArray[numIndex]; // get the value at this list index and place it in numVal
numIndex ++; // increment
}
else { timer1.Stop(); return; }
// Load the mp3 indicated by numVal
if (numVal == 1) { mediaPlayer.Open(new Uri("1.mp3", UriKind.Relative)); }
else if (numVal == 2) { mediaPlayer.Open(new Uri("2.mp3", UriKind.Relative)); }
else if (numVal == 3) { mediaPlayer.Open(new Uri("3.mp3", UriKind.Relative)); }
else if (numVal == 4) { mediaPlayer.Open(new Uri("4.mp3", UriKind.Relative)); }
else if (numVal == 5) { mediaPlayer.Open(new Uri("5.mp3", UriKind.Relative)); }
mediaPlayer.Play(); // play whats loaded
}
private void Start_Button_Click(object sender, RoutedEventArgs e)
{
numIndex = 0;
timer1.Tick += Metronome_Run; // run this at each tick
timer1.Interval = TimeSpan.FromMilliseconds(10000 / (tempo / 6));
timer1.Start();
}
}
}

Answer 1

Solved!
I moved "timer1 = new DispatcherTimer();" from the mainwindow function, and placed it in the "Start_Button_Click" event with the other timer code.
My guess is I was starting more than 1 timer with each play press, and that was causing the bug. Thanks to all who took time to look at my problem.