Yeah QB Fumbles are a real problem in this game. Basically 99% of the time that you go back to pass, and are hit as you pass, you fumble the ball. Its a redicilous call.
I see no way to fix it. Both Jameis Winston and Jared Goff have 20 fumbles over a season for me.
And I put ALL there XP into the carry attribute. Heck Goff's carry was 84 the last time I looked. Its really quite silly.