When I open the PDF file of the following article in Adobe Acrobat, the citations to the references and the figures get a popup by hovering the mouse instead of the classical hyperlink:
Li, E. Q., & Thoroddsen, S. T. (2015). Time-resolved imaging of a compressible air disc under a drop impacting on a solid surface. Journal of Fluid Mechanics, 780, 636–648. https://doi.org/10.1017/jfm.2015.466
Link to the paper.

When opening the PDF file of this article in the Zotero PDF Viewer, these popup windows appear as black rectangles and cannot be clicked: see screenshot.

This feature appears to be working only in Adobe Acrobat, so the publisher did not use this display anymore in more recent papers. It is therefore not a big problem, but it would still be good if it is possible to solve it:
- If possible, allow the popup window to work as in Acrobat.
- If it is too complicated, it would be nice to remove the black rectangle, to improve the normal reading experience, and show it in dotted line only when clicked, so that we can still guess what is the problem. This seems to be what other PDF readers are doing, for example when opened in Chrome.