PlayScore is regularly updated, and most updates include improvements to the app’s Optical Recognition engine.

When PlayScore updates itself, it does not normally reprocess your existing scores.  That means you will only see improvements in documents you create after the update, not in those created before.

Mobile:
You can easily reprocess an existing document.  Just open the document and tap the recycle symbol Recycle.  After that, playback will reflect the latest updates.