React rendering resources properly only on initial load. After that some resources dont render

Ive been having a strange problem for the past few days and I cant find a fix.
Im making a react app. Note – im using a css/bootstrap theme. And only some resources (mainly images but sometimes whole css blocks) render properly only on the initial start of the app. After that when I navigate to a different page, stuff doesnt load properly. And then when I get back to the home page – stuff is not loading properly that has loaded properly beforehand.
Ive checked the network tab and it seems im getting all the resources on the initial load. Its just strange that they dont render properly later when the router gets used.
If I want it to render properly I can only do it by refreshing the page. And then its the same again.
Im really struggling to find a fix to this, ive searched many different options but they all dont apply to my case.
Im sorry if my explanation wasnt very clear, im not that good with english.