I am not sure if you gave your textField an action to do based on the keyPressed, such as enter, but if so I bet that could possibly cause an issue.
I did what Bibhu did and it worked for me. I have a 'Go' button that the user clicks when they want to search for a card. We did drillSearchBar.getText().toLowerCase() and it works for us.
My only hypothesis would be that the textField has too many onAction scenarios firing at the wrong times with the wrong stuff in them. By actions I mean the ones in the Code section when you click the textField in Scenebuilder.