my venerable x100 is saving three copies of each shot ...

If the shutter is firing once and you are getting three you probably have film bracketing turned on. Press drive (top of command dial) and set it back to still image.
 
The command wheel and the button in the center are rather twitchy, you have to be careful. I have to use the edge of my finger on the button or I set off something I don't want.
 
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