Rockwell Automation 1771-QB Linear Pos. - Manual (Page 144)

Advanced Features
Chapter 9
9-13
Important: Incremental motion segments and relative position triggers
are based on the current axis position at the beginning of the motion
segment’s execution. Because of this, if you link a series of incremental
motion segments together you will likely see a small build-up of error. It is
recommended that an absolute position move be done occasionally to
remove this error build-up. Also, because incremental setpoint position is
based on the previous setpoint’s endpoint, but incremental motion segment
position is based on the current axis position at the beginning of the motion
segment’s execution, it is recommended that you not use a combination of
incremental setpoints and motion segments together.