You have two different problems. The instrument cluster will need to be replaced to fix the odometer as the speedometer and odometer run on the same circuit so if the speedometer is working the only thing it can be is in the instrument cluster.
The radio if working part time is most likely the radio. Check to make sure there is a good connection at the back of the radio if good replace the radio if loose repair the connection.
Basically everything you see in the dash in front of you the speedometer, gauges, idiot lights, etc. It all comes as an assembly and you need to replace it all at the same time.
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