The developer stored floating point values in a text file written out by whatever means, in the developer's locale (say en-US). These files were shipped with the application and the values were read in using locale sensitive functions on a user's machine (the developer was unaware of the locale sensitive nature of these functions), and the user's locale was something different like de-DE for example. This resulted in a different value being read in compared to the value expected by the developer, therefore causing issues in the rest of the program.
For example the file stored "1.05" which in the developer's en-US locale is "one and five hundredths", but reading it on a different user's locale (de-DE) could result in the value being "105" (one hundred and five), or even "1" (one).
These files are generally not considered to be edited by users (unless they are modding the game, and then they do so without warranty etc).