Why when I apply an orientation correction, the graph suddenly shows a displacement?

There is a bug in the correction routine. The bug bites when the 0 and 180 values for a particular depth are exactly the same. For example, the bug will bite when the A0 value and the A180 value at 9.5 meters are both 14. The bug doesn’t bit often because usually the numbers have a different sign and a different value.

The workaround is simple. Use DMM to edit the data file. Change one of the values by 1 unit. For example, change 14 to 15. That makes the problem disappear and does not affect the accuracy of the data.