Tumblr says they’ve fixed photosets posted on mobile now. They seem to however have no inclination to fix the ones that were already posted. So we have a couple of months worth of posts to fix. Note that you can only fix them on mobile.
Also it appears that any posts containing links (or maybe just posts containing a link segment) (unless the link is to YouTube) are automatically marked as spam and removed from search results. That’s what has been happening to a lot of my posts, since I like to credit the photographer properly. I’m busy removing these credit links and changing them to links in the source field and that fixes the problem for most posts. Not all though; I’m still investigating the best way to do it. Also, a lot more posts to do.
Some of these fixed posts are showing up as new posts, especially the videos, sorry about that.