On Board Computer: metric/standard

The dash computer in my 1987 six series was in metric, ex: mpg read liters, temp read celcius, etc.

Upon the first trip to my local dealer for a relay an employee inspected my car and fixed it unknown to myself until the next day I noticed it was back to standard. Which really brightened up my day by the way

But recently the car stalled and reset itself back to metric. I've tried every button combination I could think of but can't seem to right it away from its german heritage.

Any insight into how to fix or what causes the this to happen would help a lot.