Are you seeing the ball clearly? I say this because I was using some old glasses -framed almost every shot.
The next match I had some new contacts, saw the ball cleanly to the strings and didn't frame one.
So as other posters have said, keep your eye on the ball and make sure you can see it
4 Pro Staff 85 StV, 2 PS StV 110, PS Chicago 125 & 110, 3 Bab Aero Origs, 2 KPS88, Donnay X-Blue 99, Snauwaert ATP Woodforde, Hi-Ten 30