exportAsText works for some paths but returns GeneralError for others

Hello,

I am trying to make a stamp that will save the users input as a .txt file. 

I am using the exportAsText function within a trusted function and it mostly works until I try and save the output to different folders.

With the following code the output saves correctly however I don't want to save the result within the DC folder. I have changed my username to [username] in the code snippets for privacy reasons.

exportDataTotxt = app.trustedFunction( function(filename){
    app.beginPriv();
    savepath = "C:\\Users\\[username]\\AppData\\Roaming\\Adobe\\Acrobat\\DC\\"+filename;
    this.exportAsText(false,null,savepath);
    app.endPriv();
 });

When I change the savepath variable to the folllowing:

savepath = "C:\\Users\\[usermane]\\"+filename;

I get this error: 

GeneralError: Operation failed.
Doc.exportAsText:5:App Script:Calculate

I have tried with a number of different folder locations including in different drives but it only works within the DC folder.

For context the filename variable is defined in the stamp's code as follows:

filename = util.printd("ddmmyyyyHHMMss", new Date()) + "_Data.txt";