If it's a VFD (vacuum fluorescent display) it may just be tired. They get that way after many hours of use.
My van lacks a trip odometer. When I have to have precise mileage I use a GPS app on my phone that provides a resettable distance readout to 1/100 mile. While GPS isn't always identical to over-terrain distance, it's been good enough to track rally instructions. (On the plus side it's not affected by wheel slip.)
1990 E-250 Sportsmobile w/ penthouse top, converted when new by SMB Texas.