Jumping to the end of a text area in code

I have situation where I add some text to the end of a text area and set the scroll position to the end. This works fine on the Mac, and while it does add the text just fine in Windows and Linux, it doesn’t show the text when I jump to the end of the scroll position.

Anyone seen this?

I should add, it does jump to the end of the text area, but text isn’t showing until I click on the scrollbar.