Test case names containing special characters or strings like '/', '%' or '%F2' break the link in the showStackTrace (little + sign) button in the 'Failed Test Cases' section in the 'Robot results' page. Expanding the stack trace view with said button results in various errors depending on the case name, as shown in the attached image. In the image the case with '%2F' has a + button which does nothing at all. However, all off the links next to the + buttons do work.

This seems similar to the now closed JENKINS-32009, though that one seems to be about the links and not the stack trace button.