Do you have the sheet with the offset values? Itīs included with the Protrak and usually somewhere in the Protrak bag. You need that. I know at a certain time one of the values has changed with a specific ROM. From there on you will have false readings if you donīt change the values after switching to this or newer ROM. Maybe this is the problem. Look at the Protrak website. I know there are any informations regarding this. Hope it helps.