A year or so ago, every second image ad on YouTube was literal porn.

From a technical standpoint it was pretty obvious what happened. The image was overlaid with a grid of white lines. As the images were likely downsampled to reduce the required computing power, when the image was cropped right, the ML algorithm only saw a plain white image.

The only way to appeal this was a Google Support Forum where people posted screenshots and some "Gold Member Community Moderators" or whatever they were called, dismissed all complaints. They claimed that every ad was checked, porn getting through was impossible, and the people should factory-reset their phones as the only explanation was that viruses on their phone were injecting these ads...