Hello Andrew
Try giving your screen a gentle cleaning. Manually ensure that all updates are installed. Try varying the timing of tab selection (a bit longer or shorter on pressing), or use a slightly firmer touch.
Reorient Surface, sideways or even upside down. If touch in Modern IE is more effective, that could help identify problem areas for touch.
Try mapping this area with Paint, are there any spots on the screen that don't seem to react to touch so well?
Let us know of your results.
Best regards