I've worked in OER for 5+ years. What I've been told (unofficially) by people from Creative Commons and other experts is that when using a BY-SA image in a website or text document, the license does not "bubble up" and force the website or document be BY-SA.
From my understanding, the argument is that the website or document is considered a medium for distributing the image, but is not an adaptation or derivative work of the image. If the image itself was modified, that modification would have to be BY-SA.
From my understanding, the argument is that the website or document is considered a medium for distributing the image, but is not an adaptation or derivative work of the image. If the image itself was modified, that modification would have to be BY-SA.