The upside-down face emoji often shows a smile with a twist. It can mean sarcasm, awkwardness, irony, nervous humor, or "I am smiling, but this is not exactly fine."
🙃
When it appears
People use it after uncomfortable jokes, messy situations, mild embarrassment, passive sarcasm, or plans that went wrong but are still being treated lightly.
Why it is tricky
The emoji can look cheerful, but the meaning may be the opposite. It is a good example of how emoji tone depends heavily on context.
For direct frustration, the face with rolling eyes emoji may be clearer.