I moved one component off the preprocessor and the card came back as a column of unstyled text with the padding still on it, because every rule in that file whose selector started with an ampersand had quietly stopped being a rule.
A landing page needed one block to sit closer to the heading above it, and the modifier I wrote to do that had the name of a page in it.
A client spent most of a call deciding whether their green was too cold, and I spent that same call in DevTools changing the green one rule at a time.
The Sass feature that looks like it saves you bytes will quietly rewrite the order of your selectors, move your rules to a part of the file you didn't write them in, and refuse to work inside a media query.