I think your main problem is that you're swallowing exceptions, which is very bad. This is why "it works sometimes". Something is throwing an exception, and you're catching it, but then you're not doing anything else after that. At the very least I would display some sort of error message in your catch block.

A few other problems:

• Are you sure you need those multiple try..catch blocks? The current assumption in your code is that each line that is wrapped in a try..catch is independent of the others, and execution can still proceed if something goes wrong in any one (or more) of those statements. Are you sure this is what you want? If so, there is definitely a better way of handling this.
• If the statements are not independent of each other, and if a failure at any point means that execution cannot proceed, then you can wrap all of those statements in a single try..catch block and display an error message in the catch
• Like I said before, swallowing exceptions is very bad! You're hiding the problem and not achieving anything. It also makes debugging extremely hard, because things will stop working and you will have no idea why (no exception, no logging, no error messages). Exceptions are used when something unexpected happens that interrupts normal program flow. It is something you definitely want to handle.

I think what you want can be done this way:

try {
    if(window.opener.hideRecordReload){
        window.opener.hideRecordReload(pg.recordID, pg.recordTypeID);

    } else {
        window.opener.pg.hideRecord(pg.recordID, pg.recordTypeID);

    }

    window.opener.pg.hideEncounter(pg.recordID);
    window.opener.pg.hideRecordResponse(pg.hideReasonID.value == 0 ? pg.otherReason.value : pg.hideReasonID.options[pg.hideReasonID.selectedIndex].text);
    window.opener.pg.hideRecord_Response(pg.recordID, pg.recordTypeID);
    window.opener.pg.hideRecord_Response(pg.recordID, pg.recordTypeID);
    window.opener.window.parent.frames[1].pg.loadQualityMeasureRequest();
    window.opener.pg.closeWindow();

}

catch(e) {
   console.log(e);
}   

This way, if an exception occurs anywhere along those series of statements, the catch block will handle it.

Javascript also doesn't have true checked-exceptions. You can get around it by having a single try block, and inspecting the exception object that you receive^*.

Expanding on what I talked about earlier, there are two ways of handling exceptions. The first way, like I showed earlier, assumes that when an exception happens, the code is in an invalid/undefined state and this therefore means that the code encountered an unrecoverable error. Another way of handling exceptions is if you know it is something you can recover from. You can do this with a flag. So:

try {
   doSomething();
}

catch(e) {
   error = true;
}

if(error) {
   doStuffToRecoverFromError();
}

else {
   doOtherStuff();
}

In this case the flow of your logic depends on an exception being thrown. The important thing is that the exception is recoverable, and depending on whether it was thrown or not, you do different things.

^*Here is a somewhat contrived example that demonstrates checked-exceptions. I have two exceptions called VeryBadException and ReallyBadException that can be thrown (randomly) from two functions. The catch block handles the exception and figures out what type of exception it is by using the instanceof operator):

function VeryBadException(message) {
   this.message = message; 
}

function ReallyBadException(message) {
   this.message = message;
}

function foo() {
   var r = Math.floor(Math.random() * 4);
   if(r == 2) {
      throw new VeryBadException("Something very bad happened!");
   }
}

function bar() {
   var r = Math.floor(Math.random() * 4);
   if(r == 1) {
      throw new ReallyBadException("Something REALLY bad happened!");
   }
}

try {
  foo();
  bar();
}

catch(e) {
   if(e instanceof VeryBadException) {
      console.log(e.message);
   }

   else if(e instanceof ReallyBadException) {
      console.log(e.message);
   }
}

To create custom exceptions, you can inherit from the Error object:

function SpecificError () {

}

SpecificError.prototype = new Error();

// ...
try {
  throw new SpecificError;
} catch (e) {
  if (e instanceof SpecificError) {
   // specific error
  } else {
    throw e; // let others bubble up
  }
}

A minimalistic approach, without inheriting from Error, could be throwing a simple object having a name and a message properties:

function throwSpecificError() {
  throw {
    name: 'SpecificError',
    message: 'SpecificError occurred!'
  };
}


// ...
try {
  throwSpecificError();
} catch (e) {
  if (e.name == 'SpecificError') {
   // specific error
  } else {
    throw e; // let others bubble up
  }
}

The finally block contains statements to execute after the try and catch blocks execute but before the statements following the try...catch statement. The finally block executes whether or not an exception is thrown. If an exception is thrown, the statements in the finally block execute even if no catch block handles the exception. more

The finally block will always run, try returning true after your try block

function myFunc() {
     try {
         if (true) {
               throw "An error";
          }
          return true;
     } catch (e) {
          alert (e);
          return false;
     } finally {
          //do cleanup, etc here
     }
 }

There are two primary problems with that code:

1. You have a typo: var myErro = err; is missing the r on the end of myErro.

2. You're trying to use err in the finally block, but it's only in scope in the catch block.

...and then a few more that don't match what it seems like the assignment is telling you to do

3. You're not doing #1, you're doing something else which coincidentally also tries to use myVar

4. You don't have any code implementing #6.

5. Your code assigning result when there's an error is putting myErrorName and myErrorMessage literally in the string, rather than using the values of those variables.

6. Your message for when no errors have occurred is not the same as the message they told you to use, it has slight differences (including a typo). Programming is at least partially about attention to detail. :-)

You don't need if (myError == err), just if (myError) will do:

try{
  myVar();
}
catch(err){
  var myError = err;
  var myErrorName = err.name;
  var myErrorMessage = err.message;
}
 finally{
  if(myError){
    var result = "There was an error (myErrorName:myErrorMessage)";
    console.log(result);
 }else{
    console.log("No error ocurred");
 }
}

(I added a console.log so we'd see the error case.)

I've only addressed #1 and #2 in the above, the rest are left as an exercise for you to complete. :-)

I should note that I wouldn't write it that way. Declaring a variable in the catch block that you use in the finally block does work, with var (because var is not block-scoped and is hoisted), but it's misleading to people trying to maintain the code. If you're going to use a variable in both of those blocks, move the declaration outside the blocks for clarity.

Are you doing typical CRUD UI code? Use try catches, use loops that go to 10000 for no reason sprinkled in your code, hell, use angular/ember - you will not notice any performance issue.

If you are doing low level library, physics simulations, games, server-side etc then the never throwing try-catch block wouldn't normally matter at all but the problem is that V8 didn't support it in their optimizing compiler until version 6 of the engine, so the entire containing function that syntactically contains a try catch will not be optimized. You can easily work around this though, by creating a helper function like tryCatch:

function tryCatch(fun) {
    try {
        return fun();
    }
    catch(e) {
        tryCatch.errorObj.e = e;
        return tryCatch.errorObj;
    }
}
tryCatch.errorObj = {e: null};


var result = tryCatch(someFunctionThatCouldThrow);
if(result === tryCatch.errorObj) {
    //The function threw
    var e = result.e;
}
else {
    //result is the returned value
}

After V8 version 6 (shipped with Node 8.3 and latest Chrome), the performance of code inside try-catch is the same as that of normal code.