Shouldn't segments that only contain numbers, spaces, dashes and a non-translatable like 'mm' (defined in the non-translatables list) be transferred?
mm is listed via F4, so it's being recognised
The segment consisting of a number of non-translatable fragments is not the same thing as the non-translatable segment. However, you can define a non-translatable segment that does not contain any alphanumeric characters:
in your list of non-translatable fragments.
Let me try to enhance this for the most common SI units (mm, °C, kg etc.)