Many years ago I was working on a device driver for a position sensor. After deployment the customer complained that every time they started another process on

Many years ago I was working on a device driver for a position sensor. After deployment the customer complained that every time they started another process on the monitoring machine where the driver was installed the position sensor readings registered a slight movement of the object the position sensor was attached to. The object was about 20m away from the monitoring machine and weighed many tons (20?). After hearing the report I remarked that it looked like the first ever documented case of telekinesis. They were not amused. After a cross-continent trip to the customer site to instrument everything it turned out that due to the physics of the sensor (ultrasound waves traveling in a metal rod, reflecting from a magnet) the exact reading was slightly sensitive to the time elapsed from the previous reading, which in turn depended on the CPU load on the host machine. I fixed that in the driver by making sure the probing of the sensor happened in fixed time intervals, independent of the sensor reading frequency from the user space.