What do I do about exception catchers in Assembly?

[BioGoji1989]

I tried opening 03a-oldmombasa to attempt modding it, and this came up.

System.ArgumentException: Invalid index table header magic
at Assembly.Metro.Controls.PageTemplates.Games.HaloMap.<>c__DisplayClass26_1.<InitalizeMap>b__0()
at System.Windows.Threading.DispatcherOperation.InvokeDelegateCore()
at System.Windows.Threading.DispatcherOperation.InvokeImpl()
--- End of stack trace from previous location where exception was thrown ---
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Windows.Threading.DispatcherOperation.Wait(TimeSpan timeout)
at System.Windows.Threading.Dispatcher.InvokeImpl(DispatcherOperation operation, CancellationToken cancellationToken, TimeSpan timeout)
at System.Windows.Threading.Dispatcher.Invoke(Action callback, DispatcherPriority priority, CancellationToken cancellationToken, TimeSpan timeout)
at System.Windows.Threading.Dispatcher.Invoke(Action callback)
at Assembly.Metro.Controls.PageTemplates.Games.HaloMap.InitalizeMap()
at Assembly.Metro.Controls.PageTemplates.Games.HaloMap.initalLoadBackgroundWorker_DoWork(Object sender, DoWorkEventArgs e)
at System.ComponentModel.BackgroundWorker.OnDoWork(DoWorkEventArgs e)
at System.ComponentModel.BackgroundWorker.WorkerThreadStart(Object argument)

I had actually tried modding the map the previous day, but after exiting out the Assembly and starting up Halo 2, none of the changes I made appeared in the modded map during gameplay. When I closed out Halo 2 and ran assembly again, the message above was what I received each time I tried to open the map again.

 

[General_101]

You fucked up your map. Replace it

 

[BioGoji1989]

I did, and I still get the exception message. I don't know what I'm doing wrong here. Maybe I need to restart the computer so that Assembly reads the replacement map properly?

Also, the replacement map was one of the untouched backups I made of the Vanilla maps.