Yandex reverse search seems to result in an error when searching materials from tumblr now. They work perfectly if I upload it manually, but not when I supply a tumblr link.

Try this tumblr link for troubleshooting purposes: https://64.media.tumblr.com/b034de2ecd5003fc3113fabb23c15668/9b3c7b7f4d187fce-90/s500x750/b0fa687ddba92830cde4dddd2b10f1c57c689979.gif