Quoted from VonPinball:It's hard to get it in the mouth without a direct, hard hit ball, as others have noted. I have everything set on default.
It needs to be a clean shot but in no way should be "hard". Do you have a video you can post?
There are numerous adjustments both in-menu and physically. You can fine tune the home position bias to make sure it is coming down in the center of the ramp (the last 3 game adjustments are for this)
There is also a physical height adjustment on the vertical motor bracket. The jaw should just barely make contact with the ramp. To test go into diag-game-vertical motor test. Lower the trex to the lowest position. If you hit the start button the jaw will toggle open and close.
If the ball goes into the mouth but doesn't grab try removing the spacers on the clear roof plastic at the front of the ramp. This is there to make sure the ball trips the ramp optic in order to fire the mouth magnet.