Well to be fair consider the type of player who is running at your KR:
http://i221.photobucket.com/albums/dd314/tpaterniti/Stevetasker-1.pngFor starters he weighs 120 lbs more than your returner. He also has only 9% less Force Fumble Chance than you have Avoid Fumble Chance, maybe less since you probably don't actually have 30%, and he also has 6 more Tackling than you have Carrying, which is magnified by STer and Power Tackler, he also has 10 Head Hunter, 11 Monster Hit, which with the new changes now has a chance to have a double impact to fumble forcing per:
Originally posted by Changelog
Power tackling style now has a chance to double the strength of big hit, monster hit, and big sack force fumble bonuses
These are the types of gunners running at your returner. Cover Up helps a lot, Confidence should be a minimum of 60 or you will be a fumble machine, KR Specialist won't do anything for fumbles. Having said that, sometimes you do get RNGed and it just sucks, and once it happens your guy is much more likely to fumble again. So I guess I am saying there is probably a build related reason why it happened, not necessarily your build but the ones you are facing, but sometimes even if your build is perfect you still lose out, and if that was the case then I sympathize.