IMO, inconsistent spine is a major issue with carbons and, like Bob H said, if you're on the high end of the shafts' spine class the problem is magnified. Also, carbons do lose some stiffness after they've been used some. That's why when you look at the chart for a carbon arrow and see you're within 5 pounds of needing the next size up, ALWAYS go to the next size up.

Then there is straightness. An arrow shaft with +/-.006 straightness simply does not shoot as accurately as an arrow with +/-.003 or better straightness. Of course, skill level plays a part there. I guess many people simply can't shoot good enough to see the difference between junk and premium arrows.

Inside diameters aren't very consistent with carbon arrows. Some inserts are very snug when you install them, some are loose and sloppy. The loose, sloppy ones can easily be installed crooked, and a crooked insert will make it nearly impossible to get broadheads to spin true. Same thing can happen on the nock end as well. A nock that isn't properly aligned with the shaft will cause the string to launch that arrow at an angle to the line of sight. If both nock AND insert are misaligned.... Hopeless.

Arrow speed... The faster the arrow is flying, the more any problems you have with your arrow will be magnified. Wind resistance for a subsonic projectile increases at the cube of the projectile's speed. So, with any misalignment in the broadhead will cause an arrow at 270 fps to plane far worse than that same problem in an arrow at 220 fps. More wind resistance against a misaligned surface will push that surface further off it's line of travel. Hope that makes sense.

So, a heavier arrow will fly slower and reduce the effects of those problems. But the real answer is to get consistent arrows to begin with. Aluminums and ACC's are far more consistent than any ICS type carbon arrow yet made.

Then there is the question of fletching size/type. Are you using enough fletch to properly control your broadheads? Larger fletching (steerage) at the tail end of the arrow can help counteract broadhead steerage (planing) at the front end. Also, switching from vanes to feathers and/or increasing the amount of helical/offset can create more tail end steerage and make the arrows shoot straighter. Not straight, just straighter.

The root cause(s) for the planing has to be addressed in order to completely cure the problem. After several years of struggling with carbons, and since I can't afford to use ACC's on a regular basis, what I decided to do is to continue using aluminum arrows. I also use the heavier, thick walled and more durable shafts than the light, beer can thin ones that get bent and dinged up so easy. Confining my hunting shots to 30 yards and less, trajectory is simply not an issue, and the weight of those arrows make the shot whisper quiet. Not to mention the additional force the heavier arrow has when the it makes contact.

Carbon arrows do have certain advantages, which is why I've tried so desperately to get them to work for me, and wasted hundreds of dollars in the process. I'm totally dissatisfied with the quality I've seen.

There is one carbon/glass composite arrow that I do like: Carbon Express Terminator Selects. I like the weight. I like the quality. If I'm not shooting aluminum - or wood - arrows, that's what is in my quiver.