Forum Discussion
Word styles
Usually, paragraph styles wouldn't change like that. However, there are some properties of styles that can cause (seemingly) unexplained changes. For example, if a style is based on another style and the "parent" style changes, the "child" may change as well. Another possibility is that the style is set to update automatically, which means that its font (for example) changes as you apply a different font to text formatted in that style.
It is difficult to tell what has happened with your specific document. If you want to, you can share a sample document.
When setting up numbered styles it is especially important that you follow the instructions at https://shaunakelly.com/word/numbering/numbering20072010.html (Word for Windows) or https://www.brandwares.com/bestpractices/2016/06/outline-numbering-in-word-for-os-x/ (Word for Mac).