Seeing as there's an influx of reports in the last day, there's a chance Google changed something on YouTube. I wonder if they're finally pushing out video ads that can't be skipped nor blocked (without breaking video content, due to ads being loaded from the same domain(s) as the video content itself)? Or is it something like channel ads for merch or if viewing an artist/band's videos you're seeing concert dates? Having some screenshots could help with this.
Try update to Nightly version and check again.