When you add an element to a DOM structure, it automatically gets styled, based on existing CSSOM (the entirety of CSS rules from the combined loaded stylesheets).
Therefore, reloading an already loaded stylesheet is unnecessary as it will not affect the outcome of the rendering process as it already is.
Your description, that elements get some styling if already in DOM structure at a particular moment or a different styling if they get added later on, is of a behavior specific to JavaScript, which can dynamically modify DOM, apply or delete classes and/or element attributes.
However, even if dynamically modified by JavaScript, a thorough comparison of the initial elements and the ones added later on, will allow determining the specific differences generating the difference in outcome.
In other words, the problem you are trying to solve by reloading CSS is clearly not solvable by reloading the CSS. I say clearly because that's how CSS works. There's actually no way around it. CSS always applies, it does so by very specific rules, even though sometimes they might seem less than obvious and other times they might influence one another in less than (or even counter) intuitive ways.
I suggest you provide more context and detail to your specific problem so that it could be understood, its cause could be determined and solutions could be ensued. Ideally you should provide a minimal, complete and verifiable example, specifying in clear what is the desired outcome, and/or any specific preconditions required to reproduce the issue.