I manage a few sites that had Yoast previously installed and left it alone. They aren’t sites that I do much for, except keep the software updated and the occasional content addition, so I don’t pay much attention to Yoast. However, two sites had default settings indicating they could have been affected by this issue. I updated the setting to their new recommendation. It has to do with media files.
I know Yoast has a nice interface and lots of features, but it is also somewhat bloated and according to some SEO experts, doesn’t deliver the best results.
I recommend All-In-One SEO instead. Even the free version has great features.
While I don’t pretend to be an SEO expert, if you’re on the fence about which plugin to use, this could sway your choice a bit.