So I started to investigate the issue and couldn't find the reason for such issue.
Inside the log file C:\SWSoft\SiteBuilder\_logs\Application.log I found the following:
2008-05-27 20:19:21,156 [5] DEBUG SWsoft.SiteBuilder.Repository.Site.RepositoryWrapper - Complete loading site repository [#00186594-49fe-4a97-8f2d-908b59eac686].
2008-05-27 20:19:21,390 [5] DEBUG SWsoft.SiteBuilder.BO.Facade.Publish.LocationChecker - LocationChecker.Execute()
2008-05-27 20:19:21,390 [5] DEBUG SWsoft.SiteBuilder.BO.Facade.Publish.LocationChecker - Create folder in root folder: TestFolder0749c788-e392-4edd-a678-3b1602ab16aa
2008-05-27 20:19:21,609 [5] DEBUG SWsoft.SiteBuilder.Repository.FtpResources.XceedFtpClient - XceedFtpClient.Connect() for ServerIP:21
2008-05-27 20:19:21,812 [5] DEBUG SWsoft.SiteBuilder.Repository.FtpResources.XceedFtpClient - XceedFtpClient.ServerFolderSeparator is '/'
2008-05-27 20:19:21,828 [5] DEBUG SWsoft.SiteBuilder.Repository.FtpResources.XceedFtpClient - XceedFtpClient.List() for path ''
2008-05-27 20:19:22,031 [5] DEBUG SWsoft.SiteBuilder.Repository.FtpResources.XceedFtpClient - XceedFtpClient.Ensure() for path 'TestFolder0749c788-e392-4edd-a678-3b1602ab16aa'
2008-05-27 20:19:22,078 [5] DEBUG SWsoft.SiteBuilder.BO.Facade.Publish.LocationChecker - Remove folder in root folder: TestFolder0749c788-e392-4edd-a678-3b1602ab16aa
2008-05-27 20:19:22,093 [5] DEBUG SWsoft.SiteBuilder.Repository.FtpResources.XceedFtpClient - XceedFtpClient.RemoveDirectory() called for 'TestFolder0749c788-e392-4edd-a678-3b1602ab16aa'
2008-05-27 20:19:22,218 [5] DEBUG SWsoft.SiteBuilder.BO.Facade.Publish.LocationChecker - LocationChecker.CheckCaseSensitivity()
2008-05-27 20:19:22,250 [5] DEBUG SWsoft.SiteBuilder.Repository.FtpResources.XceedFtpClient - XceedFtpClient.List() for path ''
2008-05-27 20:19:22,562 [5] DEBUG SWsoft.SiteBuilder.Repository.FtpResources.XceedFtpClient - XceedFtpClient.Ensure() for path 'CASETEST27EE0022-E8CC-4858-8413-70ED05DC26A5'
2008-05-27 20:19:22,593 [5] DEBUG SWsoft.SiteBuilder.Repository.FtpResources.XceedFtpClient - XceedFtpClient.RemoveDirectory() called for 'CASETEST27EE0022-E8CC-4858-8413-70ED05DC26A5'
2008-05-27 20:19:22,640 [5] DEBUG SWsoft.SiteBuilder.Repository.FtpResources.XceedFtpClient - XceedFtpClient.RemoveDirectory() called for 'casetest27ee0022-e8cc-4858-8413-70ed05dc26a5'
2008-05-27 20:19:22,640 [5] DEBUG SWsoft.SiteBuilder.BO.Facade.Publish.LocationChecker - End LocationChecker.CheckCaseSensitivity()
2008-05-27 20:19:22,656 [5] DEBUG SWsoft.SiteBuilder.BO.Facade.Publish.LocationChecker - LocationChecker.PublishProbeFiles()
2008-05-27 20:19:22,656 [5] DEBUG SWsoft.SiteBuilder.BO.Facade.Publish.LocationChecker - Create test folder: Test14d77632-715a-4cf6-93a2-a50eca8d270d
2008-05-27 20:19:22,656 [5] DEBUG SWsoft.SiteBuilder.Repository.FtpResources.XceedFtpClient - XceedFtpClient.List() for path ''
2008-05-27 20:19:22,750 [5] DEBUG SWsoft.SiteBuilder.Repository.FtpResources.XceedFtpClient - XceedFtpClient.Ensure() for path 'Test14d77632-715a-4cf6-93a2-a50eca8d270d'
2008-05-27 20:19:22,765 [5] DEBUG SWsoft.SiteBuilder.Repository.FtpResources.XceedFtpClient - XceedFtpClient.List() for path 'Test14d77632-715a-4cf6-93a2-a50eca8d270d'
2008-05-27 20:19:22,796 [5] DEBUG SWsoft.SiteBuilder.Repository.FtpResources.XceedFtpClient - XceedFtpClient.Upload() for path 'Test14d77632-715a-4cf6-93a2-a50eca8d270d\test.html'
2008-05-27 20:19:22,859 [5] DEBUG SWsoft.SiteBuilder.Repository.FtpResources.XceedFtpClient - XceedFtpClient.List() for path ''
2008-05-27 20:19:22,984 [5] WARN SWsoft.SiteBuilder.BO.Facade.Publish.LocationChecker - Publish Location checker, PublishProbeFiles step error
System.ArgumentException: An item with the same key has already been added.
at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
at SWsoft.SiteBuilder.Repository.Resources.ResourceItemsCollection`2.FillChildren()
at SWsoft.SiteBuilder.Repository.Resources.ResourceItemsCollection`2.Contains(String name)
at SWsoft.SiteBuilder.BO.Facade.Publish.LocationChecker.PublishResourceFile(IResourceFolder targetFolder, String name, String resourceName)
at SWsoft.SiteBuilder.BO.Facade.Publish.LocationChecker.PublishProbeFiles()
2008-05-27 20:19:22,984 [5] DEBUG SWsoft.SiteBuilder.BO.Facade.Publish.LocationChecker - LocationChecker.DeleteProbeFiles()
2008-05-27 20:19:22,984 [5] DEBUG SWsoft.SiteBuilder.BO.Facade.Publish.LocationChecker - Try to remove
2008-05-27 20:19:22,984 [5] DEBUG SWsoft.SiteBuilder.Repository.FtpResources.XceedFtpClient - XceedFtpClient.List() for path 'App_Data'
2008-05-27 20:19:23,062 [5] DEBUG SWsoft.SiteBuilder.BO.Facade.Publish.LocationChecker - End LocationChecker.DeleteProbeFiles()
2008-05-27 20:19:23,062 [5] DEBUG SWsoft.SiteBuilder.BO.Facade.Publish.LocationChecker - Remove test folder Test14d77632-715a-4cf6-93a2-a50eca8d270d
2008-05-27 20:19:23,062 [5] DEBUG SWsoft.SiteBuilder.Repository.FtpResources.XceedFtpClient - XceedFtpClient.RemoveDirectory() called for 'Test14d77632-715a-4cf6-93a2-a50eca8d270d'
2008-05-27 20:19:23,328 [5] ERROR SWsoft.SiteBuilder.Web.PublishUtil - Unknown error occured
SWsoft.SiteBuilder.BO.Facade.PublishException: Publish failed: unknown exception ---> System.ArgumentException: An item with the same key has already been added.
at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)
at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
at SWsoft.SiteBuilder.Repository.Resources.ResourceItemsCollection`2.FillChildren()
at SWsoft.SiteBuilder.Repository.Resources.ResourceItemsCollection`2.Contains(String name)
at SWsoft.SiteBuilder.BO.Facade.Publish.LocationChecker.PublishResourceFile(IResourceFolder targetFolder, String name, String resourceName)
at SWsoft.SiteBuilder.BO.Facade.Publish.LocationChecker.PublishProbeFiles()
at SWsoft.SiteBuilder.BO.Facade.Publish.LocationChecker.Execute()
at SWsoft.SiteBuilder.BO.Facade.SiteService.<>c__DisplayClassd.<CheckPublishLocation>b__a()
at SWsoft.SiteBuilder.BO.Facade.PublishHelper.CheckPublishExceptions(CheckPublishExceptionsMethod a_method)
at SWsoft.SiteBuilder.BO.Facade.PublishHelper.CheckPublishExceptionsWithAny(CheckPublishExceptionsMethod a_method, PublishMode a_mode)
--- End of inner exception stack trace ---
at SWsoft.SiteBuilder.BO.Facade.PublishHelper.CheckPublishExceptionsWithAny(CheckPublishExceptionsMethod a_method, PublishMode a_mode)
at SWsoft.SiteBuilder.BO.Facade.SiteService.CheckPublishLocation(Guid siteId, PublishingSettingsValue publishingSettings)
at SWsoft.SiteBuilder.Web.UI.WebControls.SiteView.ButtonStandardVerifyLocation_OnClick(Object sender, EventArgs e)
2008-05-27 20:19:25,703 [6] DEBUG SWsoft.SiteBuilder.BO.Facade.StatisticsService - StatisticsService.AddSessionTrack()...
2008-05-27 20:19:25,703 [6] DEBUG SWsoft.SiteBuilder.BO.Facade.StatisticsService - ...completed StatisticsService.AddSessionTrack()