After an update either from within ST or from the installer (tried both ways) the application becomes unable to launch.  I blow out the new 2899 folder and then I am able to launch the older version.  I have searched windows event logs, only thing I find is in the sourcetree.log:

ERROR [2019-03-04 09:42:06,090] [1] [SourceTree.App] [Log] - Failed to start
System.NullReferenceException: Object reference not set to an instance of an object.
at SourceTree.AppRoot.DoWindowStartupTasks()
at SourceTree.ViewModel.MainWindowViewModel.DoStartupTasks()
at SourceTree.ViewModel.MainWindowViewModel..ctor(IRepositoryTabContainerViewModel repositoryTabContainerViewModel, ICustomActionsManager customActionsManager, IRepositoryManager repositoryManager, IAnalyticsDataManager analyticsDataManager, ITraceManager traceManager, IDispatcher dispatcher, IAccountManager accountManager, IFailureHandler failureHandler, IDvcsManager dvcsManager, IConfigurationManager configurationManager, IInstanceManager instanceManager, ISchedulerManager schedulerManager, IWebManager webManager, IRepositoryMonitorManager repositoryMonitorManager, ISshKeyManager sshKeyManager, INotificationsManager notificationsManager, IPreferencesManager preferencesManager, IRepoProcessFactory repoProcessFactory, IBookmarkManager bookmarkManager)
at SourceTree.MainWindow..ctor(IRepositoryTabContainerViewModel repositoryTabContainerViewModel, ICustomActionsManager customActionsManager, IRepositoryManager repositoryManager, IAnalyticsDataManager analyticsDataManager, ITraceManager traceManager, IDispatcher dispatcher, IAccountManager accountManager, IFailureHandler failureHandler, IDvcsManager dvcsManager, IConfigurationManager configurationManager, IInstanceManager instanceManager, ISchedulerManager schedulerManager, IWebManager webManager, IRepositoryMonitorManager repositoryMonitorManager, IApplicationManager applicationManager, ISshKeyManager sshKeyManager, INotificationsManager notificationsManager, IBookmarkManager bookmarkManager, IPreferencesManager preferencesManager, IRepoProcessFactory repoProcessFactory)
at SourceTree.AppRoot.<OnStartup>d__31.MoveNext()
— End of stack trace from previous location where exception was thrown —
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at SourceTree.App.<OnStartup>d__4.MoveNext()
DEBUG [2019-03-04 09:42:06,121] [20] [SourceTree.Instances.SingleInstance] [Log] - SingleInstance pipe connection received
DEBUG [2019-03-04 09:42:06,121] [20] [SourceTree.Instances.SingleInstance] [Log] - SingleInstance waiting for connection: iar is not null
DEBUG [2019-03-04 09:42:06,121] [1] [SourceTree.Configuration.DefaultConfigurationManager] [Log] - Saved settings
DEBUG [2019-03-04 09:42:06,136] [1] [SourceTree.AppRoot] [Log] - Unregister crash event handlers for [SourceTree.Analytics.Crash.BugSplat.CrashAnalyticsService]
DEBUG [2019-03-04 09:42:06,136] [1] [Sourcetree.Analytics.Emau.EMauSubmissionService] [Log] - Stop submission