When harvesting row crops, there comes a time when opening fields that it's often convenient or necessary to harvest across the endrows. This puts tremendous stress on harvesting heads, especially soybean platforms.
Cutting perpendicular to the rows forces the sickle to go from "no load" between rows to total load across the full length of the cutterbar in a split second. On a 24-row headland, the sickle has to absorb that shock load 24 times in only 10 or 15 seconds. A soybean platform in good mechanical condition will probably handle the abuse without damage, but a platform with a worn sickle or drive could fail under the rapid changes in load. Typical consequence is a broken sickle or snapped drive belt halfway across the headland--or halfway down the headland or into the field as damage that began on the headland finally reached critical mass a few acres later.
Corn heads are a little tougher than cutterbar systems, but the shock load of 8 rows of Bt-corn stalks supporting 180 bu./ac. corn has been known to cause aged or worn corn heads to shear gears or make slip clutches rattle.
To avoid shock loading harvesting equipment when harvesting "across" rows, turn the combine slightly or drive in a slight curve so that each row doesn't encounter the cutterbar or gathering components all at once.