Volume Sensor fake detection

Hi there!
I am using the Volume Sensor behavior to detect collisions between the arm of a robot and the rest of its body. It’s pretty good, but sometimes (for some configurations, not at random times) it detects false collisions. I can see the volume sensor boxes, and it’s obvious that the objects do not intersect, so I don’t understand why it triggers the sensor.
Has anyone else had this issue? Is there an explanation?

Thank you!