I have a MKIII nav system in my 2001 beast. The scale setting will change by itself while I am driving. If it is set at 250 yards, it will migrate to 450 yards, then 900 yards, then 1 mile. I usually catch it by this time, so I'm not sure if would continue to the next setting or not. Also, I haven't played with it enough to see if it happens at certain time intervals, or if it is related to car speed. I was just wondering if this is normal?