In my opinion, WV Hunter and Arthur P have possibly identified the problem.

The spine of your shafts may be incorrect or too near the "redline" and the mech heads allowed you to get by.

If you are shooting carbons; regardless of the range of spine carbons allow …which I personally do not agree with…. and believe the manufacturer's hype has sold the goods, you may have been too close to need in more or less spine. If you are shooting aluminum shafts, a jump to 125 from 80 is too much unless you drop your draw-weight…a lot.

A misconception by many shooters is that if the spine of a shaft is correct for field tips so will it be for broadheads. In some cases it (spine) will be ok, in a lot of cases it won't be. Not only can the flight of a broadhead mounted shaft be affected by wind planing, the forces that are being put upon the "winged" broadhead can cause a spine issue.

Arthur P is also correct about checking with the outfitter. Many have strict rules about what equipment and setup is allowed/required. One well-known outfitter for Africa hunts not only does not allow mechs, he also does not allow Muzzy's.

PS: Alignment of fletch with blades does nothing but make the shooter feel better about his/her setup.