Here’s a silly thought: sort of like Sherlock Holmes’s "When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth .”…
The C172 is fuel injected so carb icing SHOULDN’T exist (or even be possible), but maybe the model is incorrect? Just seeing the ice on the windshield made me wonder. In real life, carb icing should also not be an issue at temperatures that low, but who knows what is modeled?
Two possible tests:
- Try the keyboard shortcut for carb heat (because the aircraft does not have a carb heat lever) for a while at high power and try again without it
- Go for custom weather and bump up the temperature to +20°C and try again
I know this is unlikely to the point of absurdity, but nothing else jumps out.