P: Script Metadata assignment error

The  following statement in my script below works in Photoshop version Prior to CC 2015.5 but not in  CC 2015.5 Scripting. 

app.activeDocument.info.instructions = before + after;


The full simple toggle script is here

/* ======================================================================================// 2015  John J. McAssey (JJMack)  http://www.mouseprints.net/
//  
// This script is supplied as is. It is provided as freeware. 
// The author accepts no liability for any problems arising from its use.
//
// This script is designed to Toggle centering guides 
//
// ===================================================================================== */
/*

$$$/JavaScripts/AddRemoveCenterGuides/About=JJMack's AddRemoveCenterGuides.^r^rCopyright 2009 Mouseprints.^r^rRun twice script utility for action.^r^rFirst Run Set Guides on camvas bounds and center.^rSecond Run clears the set guides.
JJMackJJMack's Action Run Twice Utility

*/
if (app.documents.length > 0) app.activeDocument.suspendHistory('ToggleCenterGuides','main()' );
else alert("You must have at least one open document to run this script!"); 
/////////////////////////////////////////////////////////////////////////////////////////// 
function main() { 
if (app.activeDocument.info.instructions.indexOf("") == -1 ){ // no footprint fisrt useage 
var orig_ruler_units = app.preferences.rulerUnits;
app.preferences.rulerUnits = Units.PIXELS; // Set the ruler units to PIXELS
try { 
activeDocument.guides.add(Direction.VERTICAL, 0);
activeDocument.guides.add(Direction.VERTICAL, activeDocument.width/4);
activeDocument.guides.add(Direction.VERTICAL, activeDocument.width/2);
activeDocument.guides.add(Direction.VERTICAL, activeDocument.width*3/4);
activeDocument.guides.add(Direction.VERTICAL, activeDocument.width);
activeDocument.guides.add(Direction.HORIZONTAL, 0);
activeDocument.guides.add(Direction.HORIZONTAL, activeDocument.height/4);
activeDocument.guides.add(Direction.HORIZONTAL, activeDocument.height/2);
activeDocument.guides.add(Direction.HORIZONTAL, activeDocument.height*3/4);
activeDocument.guides.add(Direction.HORIZONTAL, activeDocument.height);
  }
// display error message if something goes wrong
catch(e) { alert(e + ': on line ' + e.line, 'Script Error', true); }
app.preferences.rulerUnits = orig_ruler_units; // Reset units to original settings
// put footprint in metadata info instructions
app.activeDocument.info.instructions = app.activeDocument.info.instructions + "" + " Show" + ""; 
} 
else { 
clearGuides();
// Remove footprint from metadata info instructions
before = app.activeDocument.info.instructions.substr(0,app.activeDocument.info.instructions.indexOf(""));
afterOffset = app.activeDocument.info.instructions.indexOf("") + "".length;
after = app.activeDocument.info.instructions.substr(afterOffset, app.activeDocument.info.instructions.length - afterOffset);
//alert ("before = " + before + " after = " + after);
app.activeDocument.info.instructions = before + after;
} 
} 
//////////////////////////////////////////// Action Manager Code to Clear all Guides ///////////////////////////////////
function clearGuides() { 
   var id556 = charIDToTypeID( "Dlt " ); 
       var desc102 = new ActionDescriptor(); 
       var id557 = charIDToTypeID( "null" ); 
           var ref70 = new ActionReference(); 
           var id558 = charIDToTypeID( "Gd  " ); 
           var id559 = charIDToTypeID( "Ordn" ); 
           var id560 = charIDToTypeID( "Al  " ); 
           ref70.putEnumerated( id558, id559, id560 ); 
       desc102.putReference( id557, ref70 ); 
   executeAction( id556, desc102, DialogModes.NO ); 
};