It seems to be an issue with “Set Reading order to last”. Although this sets the tocs (and all the other elements with it) to the end of the Dom, it does not influence the z-index, i.e. although the toc is the last element to be read, it keeps its z-index of e.g. “8”, meaning its behind the page elements. For some reasons I can’t find, the second toc gets a higher z-index and is above the page. With no accessibility requirements you’d set it “Always on top” which would solve it.
Does the z-index influence accessibility? If I add CSS to raise the z-index for both tocs, it’ll be displayed correctly .