If the trip odometer doesn't maintain the mileage, it's usually a blown fuse for the CIG CLK or radio memory circuit. There has to be a memory power feed to the dash at all times to maintain odometer readings AND to keep in MPH or KPH everytime you start the car. If the MPH and KPH toggles once in a while, the memory fuse is out.
Also, your radio won't keep the stations in memory if it's dead.