v01-2.0.8 Printing surface calibration failed

[gedsHuster]

When I calibrate the print surface of the BCN3D Sigma, the limit switch of the left nozzle is not touching the platform. This caused inaccurate calibration results.
I thought it was a firmware problem, yesterday I upgraded the firmware version to 2.0.8, but the problem was still not solved.

Details of the problem：
When my Sigma printer is automatically calibrating the print surface, the limit switch of left nozzle is not touching the left rear of the platform (site of away from the user). The platform stops moving upwards without the limit switch of the left nozzle being touched. And the left nozzle immediately move to the left front and right front of the platform, ready to contact with the platform. The nozzle in these two positions is basically no problem, the platform moved upward twice, the platform did not touch the limit switch at the first time , but touched on the second time.