The icons that display for files in Windows are saved in an icon cache so they can be displayed quickly instead of having to manually scan and slowly load them each time. The icon cache can sometimes become corrupted causing the icons of files to display incorrectly or distorted. When this...
Could be a problem with either the "Segoe MDL2 Assets" font or the "Segoe Fluent" font.
Check the fonts are present in Settings > Personalisation > Fonts, then under Available fonts, type 'Segoe' into the search box, and see if both fonts appear in the search results.
Do the buttons still work when you click on them, is it just a font issue?