MGSM1600GY detecting issue

We use two MGSM1600GY line following sensors, the analog outputs are connected to the plc.
The other communication outputs of the sensor are not used.
It worked well on the table, but as we mounted it on the AGV robot, the sensor began to detect incorrectly.
This can be caused by the iron structure in the soil.
Do you have any idea how to avoid this?