The machine was some laptop mainboard glued to the backside of my monitor, and the USB socket came out at the top of the mainboard. On its way down, the USB cable for the keyboard passed across the whole mainboard. On high load, the mainboard created enough interference to cause the connection to reset, re-hotplugging my keyboard, so the previous setxkbmap call was not effective anymore and i was back to the standard US qwerty layout.