java.awt.Robot is unable to paste long strings

I use Robot class to paste strings from clipboard to file chooser dialog window in a loop. Strings are file paths, so these are 100-180 characters long. After the first few strings it is unable to paste more. The same solution is working well with shorter strings.

StringSelection ssss = new StringSelection(fileSource);
Toolkit.getDefaultToolkit().getSystemClipboard().setContents(ssss, null);
Robot probot = new Robot();
probot.keyPress(KeyEvent.VK_CONTROL);
Thread.sleep(2000);
probot.keyPress(KeyEvent.VK_V);
Thread.sleep(2000);
probot.keyRelease(KeyEvent.VK_V);
Thread.sleep(2000);
probot.keyRelease(KeyEvent.VK_CONTROL);
Thread.sleep(2000);
probot.keyPress(KeyEvent.VK_ENTER);
probot.keyRelease(KeyEvent.VK_ENTER);

Might I suggest moving the below statement outside (above) your for loop.

Robot probot = new Robot();
for (int cnt = 0;...

I assume you are getting a new fileSource each time through the loop so you likely need that, but if it is the same, then put that outside the for loop too.

Can I also suggest a slight change to remove a couple of the delays you have?

probot.keyPress(KeyEvent.VK_CONTROL);
probot.keyPress(KeyEvent.VK_V);
Thread.sleep(2000);
probot.keyRelease(KeyEvent.VK_V);
probot.keyRelease(KeyEvent.VK_CONTROL);