I've had a bug in linux driver for a very shitty touchscreen we used in our embedded devices. It needed manual calibration and you had to save the calibration

I've had a bug in linux driver for a very shitty touchscreen we used in our embedded devices. It needed manual calibration and you had to save the calibration matrix in a config file read on system startup. They used locale-aware input function in a driver so when the locale was German (or other with "," as a decimal separator) it broke and users got kernel panic at startup :) It bricked all our devices in Germany. We worked around it, notified the device driver developers and forgot about it. A year later we shipped with new version of kernel and it broke again - because the bug was fixed in kernel and our workaround was now causing the bug :)