CMAX Rear Window Heating Issue

That's quite a pickle! Sounds like a power issue. A weak battery can cause all sorts of electrical gremlins in modern cars. Is the engine cranking slower than usual when you start it? Have you tried measuring the battery voltage?

Engine seems to start normally, no noticeable delay. I haven't measured the battery voltage yet. If the engine starts normally, could the battery still be the root of the rear defroster malfunction?

It's less likely if the engine starts normally, but still possible. Think of it like a water faucet - you might have enough pressure for a trickle, but not enough for a full blast. Modern cars are sensitive, and even a slightly underperforming battery can cause issues with specific systems like the rear defroster. Getting it checked at a workshop would be the best move.

I had the battery tested, and it was indeed heavily discharged. Replacing it resolved the issue with the rear window heating. Total repair cost was 290€. Thanks again for your assistance.