@Unsounded Hmm, besides the unusual formatting (is this a problem of the code tag in this forum?) of your code the only odd thing I currently see is the line

string szName = String.Format("{0:}{2}.{3}", "", szBase, mk.Name, rend.Extension);

After the colon (in the first placeholder) should be followed by formatString (for example yyyy, if you only want the four digit year of a date value). But yours is simply empty and the {0:} gets then replaced by "", so it's not even necessary. I could simply look like

string szName = String.Format("{2}.{3}", "", szBase, mk.Name, rend.Extension);

I don't think that should have any influence on the way RenderAs works. But I don't know if the Sound Forge Compiler is any way unique and may have a problem with that.

Here I try a better formatting. I'm currently on my phone so this might not be perfect:

using System;
using System.IO;
using System.Windows.Forms;
using SoundForge;

//Run with a file that contains regions
//Iterates through the regions, renders to PCA and saves the rendered file to c:\media\rip
//Scan the file for MODIFY HERE to see how to quickly customize for your own use

public class EntryPoint {
public string Begin(IScriptableApp app) {

   //start MODIFY HERE-----------------------------------------------
   string szType  = GETARG("type", ".mp3"); //choose any valid extension: .avi  .wav  .w64 .mpg .mp3 .wma .mov .rm .aif .ogg .raw .au .dig .ivc .vox .pca
   object vPreset = GETARG("preset", "Vocab For Web"); //put the name of the template between the quotes, or leave blank to pop the Template chooser. 
   string szDir   = GETARG("dir", ""); //hardcode a target path here

   // GETARG is a function that defines the default script settings. You can use the Script Args field to over-ride
   // the values within GETARG().
   // Example: To over-ride GETARG(Key, valueA), type Key=valueB in the Script Args field.
   //          Use an ampersand (&) to separate different Script Args: KeyOne=valueB&KeyTwo=valueC

   //Example Script Args: type=.wav&dir=f:\RegionFiles

   //end MODIFY HERE -----------------------------------
    
    ISfFileHost file = app.CurrentFile;
    ISfDataWnd wnd = app.ActiveWindow;

   if (null == file)
      return "Open a file containing regions before running this script. Script stopped.";
   if (null == file.Markers || file.Markers.Count <= 0)
      return "The file does not have any markers.";

    // Save file first
    app.DoMenuAndWait("File.Save", false);

    //bool showMsg = true;
    if (!File.Exists(@"C:\Temp\#loc.txt"))
    {
          bool showMsg = true;
            if (szDir == null || szDir.Length <= 0)
            {
                szDir = PromptForPath(@"L:\Text to speech\#auto");
                showMsg = false;
            }
            if (szDir == null || szDir.Length <= 0 || showMsg)
            {
                MessageBox.Show(String.Format("No output directory - operation cancelled!", szDir), "Oops!", MessageBoxButtons.OK, MessageBoxIcon.Information);
                return "No output directory - operation cancelled!";    
            }        
    }
    else
    {
        // Open regionPath.txt
        StreamReader current = new StreamReader(@"C:\Temp\#loc.txt");

        // read last used path
        szDir = current.ReadLine().Trim();

        current.Close();
    }
    
   //make sure the directory exists
   if(!Path.IsPathRooted(szDir))
   {
      string szBase2 = Path.GetDirectoryName(file.Filename);
      szDir = Path.Combine(szBase2, szDir);
   }

   Directory.CreateDirectory(szDir);

   ISfRenderer rend = null;
   if (szType.StartsWith("."))
       rend = app.FindRenderer(null, szType);
   else 
       rend = app.FindRenderer(szType, null);

   if (null == rend)
   return String.Format("renderer for {0} not found.", szType);

   // if the preset parses as a valid integer, then use it as such, otherwise assume it's a string.
   try {
       int iPreset = int.Parse((string)vPreset);
       vPreset = iPreset;
   } catch (FormatException) {}

   ISfGenericPreset template = null;
   if ((string)vPreset != "")
      template = rend.GetTemplate(vPreset);
   else   
      template = rend.ChooseTemplate((IntPtr)null, vPreset);
   if (null == template)
      return "Template not found. Script stopped.";
       
    string szBase = file.Window.Title;

    //showMsg = true;
    foreach (SfAudioMarker mk in file.Markers)
    {
        if (mk.IsRegion)
        {
            string szName = String.Format("{2}.{3}", "", szBase, mk.Name, rend.Extension);
            szName = CleanFilename(szName,app.CurrentFile.Filename);
            
            if (szName != "!")
            {            
                DPF("Queueing: '{0}'", szName);

                string szFullName = Path.Combine(szDir, szName);
                if (File.Exists(szFullName))
                File.Delete(szFullName);

                SfAudioSelection  range = new SfAudioSelection(mk.Start, mk.Length);
                file.RenderAs(szFullName, rend.Guid, template, range, RenderOptions.WaitForDoneOrCancel );
                DPF("Path: '{0}'", szFullName);
            }    
        }
   }   

  // if(showMsg)
  // MessageBox.Show(String.Format("Files are saving to: {0}", szDir), "Status", MessageBoxButtons.OK, MessageBoxIcon.Information);
 
     //==================================================
    //Count regions and save this number to a file
    
    long countRegions = 0;
    
    foreach (SfAudioMarker mk in file.Markers)
    {
        if (mk.IsRegion)
        countRegions++;
    }
    
    System.IO.File.Delete(@"C:\Temp\#reg.txt");
    TextWriter reg = new StreamWriter(@"C:\Temp\#reg.txt");
    reg.WriteLine(szDir);
    reg.WriteLine(countRegions);
    reg.Close();
    
    //==================================================
 
   return null;
}

public string CleanFilename(string szName,string whem)
{
   szName = szName.Replace("!", "");    
   szName = szName.Replace("..", ".");  
   szName = szName.Replace("?", "");    
   szName = szName.Replace(":", " - "); 
   szName = szName.Replace('\\', '_'); 
   szName = szName.Replace('/', '_'); 
  
   foreach (char ch in System.IO.Path.GetInvalidPathChars())
   {
      szName = szName.Replace(ch, '_'); 
   }
   
   whem = whem.Replace(".mp3","");
   
   //Is it a whem wordlist?
   if (whem.Contains("Wordlists"))
   { 
       if (whem.Contains("Ryan"))
        szName = szName.Replace(".mp3","1.mp3");
        if (whem.Contains("Aria"))
        szName = szName.Replace(".mp3","2.mp3");
        if (whem.Contains("Maisie"))
        szName = szName.Replace(".mp3","3.mp3");

        szName = szName.Replace(" ","_");
        szName = szName.ToLower();
   }
   
   return szName;
}

public string PromptForPath(string szDir) {

   FolderBrowserDialog dlg = new FolderBrowserDialog();
   
   dlg.Description = szDir;        
   //if (null != szDir && "" != szDir)
      dlg.SelectedPath = szDir;
   dlg.ShowNewFolderButton = true;
   DialogResult res = dlg.ShowDialog();         
   if (res == DialogResult.OK)
      return dlg.SelectedPath;
   return null;
}

public void FromSoundForge(IScriptableApp app) {
   ForgeApp = app; //execution begins here
   app.SetStatusText(String.Format("Script '{0}' is running.", Script.Name));
   string msg = Begin(app);
   app.SetStatusText((msg != null) ? msg : String.Format("Script '{0}' is done.", Script.Name));
}
public static IScriptableApp ForgeApp = null;
public static void DPF(string sz) { ForgeApp.OutputText(sz); }
public static void DPF(string fmt, object o) { ForgeApp.OutputText(String.Format(fmt,o)); }
public static void DPF(string fmt, object o, object o2) { ForgeApp.OutputText(String.Format(fmt,o,o2)); }
public static void DPF(string fmt, object o, object o2, object o3) { ForgeApp.OutputText(String.Format(fmt,o,o2,o3)); }
public static string GETARG(string k, string d) { string val = Script.Args.ValueOf(k); if (val == null || val.Length == 0) val = d; return val; }
public static int    GETARG(string k, int d) { string s = Script.Args.ValueOf(k); if (s == null || s.Length == 0) return d; else return Script.Args.AsInt(k); }
public static bool   GETARG(string k, bool d) { string s = Script.Args.ValueOf(k); if (s == null || s.Length == 0) return d; else return Script.Args.AsBool(k); }
} //EntryPoint