Text may be positioned incorrectly if TextBox.positionCaret is used.

Attached is a small test demonstrating the problem and a screenshot.
TextBox should be displaying "12345", but only "5" is displayed as the content is shifted incorrectly.
The problem will correct itself once the TextBox is manipulated with using mouse/keyboard.

This happens in both prism and swing toolkit in Soma.
On TV this bug breaks Virtual Keyboard (see TV-693)