it is not the mount but the vibrations which affects a certain batch of Karoo 2s...I have had 2 with the same problem and they are due to some faulty hardware which they rectified in later models...

Do the same ride with the Karoo in your back pocket and see how much more accurate the total elevation becomes..

A mount which is more prone to vibrations will give a far worse reading than one mounted directly above the steerer...

It has nothing to do with blocked barometric sensor holes, wind, temp, etc....simply vibrations...

Hammerhead admitted a batch of these Karoo 2s had this problem and will replace them under warranty...unfortunately the 2nd unit I got had the same issue