PlayScore is very accurate so long as you have a good camera and as long as the photo is good!  If you have a good camera but are getting poor results, the answer is something to do with the photo. Try the following:
Use lots of light – Daylight is ideal. A flash is often counterproductive because the illumination is patchy. Stand the page up vertically – not on a horizontal surface. Make sure the music is not curled up – the flatter the better. Make sure the image is square on the screen – line the sides of the music up with the sides of the screen – make sure measure lines are vertical. Don’t cut off parts of the music – the left edge where the clefs are is especially important Make sure the focus is crisp – some cameras take a little time to focus. NB Use a phone if possible – phones have better cameras than tablets.
If one shot isn’t very good take another.  It can take a little trial and error to learn a good technique.