What could be the potential causes of errors during robot picking?

When errors occur during robot picking, what factors and causes should be checked, and in what order?

A typical 3D-guided robot picking process consists of the following steps and the corresponding errors:
(1) The 3D Vision System locates the workpieces - Vision Error
(2) The Mech-Mind Vision System transforms the poses of the workpieces from the camera reference frame to the robot reference frame - Pose Transformation Error
(3) The robot drives the gripper to pick the workpieces - TCP Error

For details of error analyses for robot picking, see Analysis of error chain for 3D-guided robot picking.