Good morning, Roger;

A less likely possiblility is a contact that pulls away when it is cold. With older equipment, this can be an uncommon problem. I have used an electrical multimeter in conductivity or "ohms" mode and sprayed some "Freeze-Mist" low temperature cooling spray on parts and pieces to try locating this kind of a thermal intermittent.

Try the new or different battery first. Taking something apart and hunting for an intermittent is never fun. There is a reason why we referred to these kind of jobs as "dogs."