On the site's start page, if I open the "modified" link of one of the listed questions in a new background tab, I sometimes end up in the footer rather than at the modifed question or answer.
For example, this link allows me to reproduce this behavior at will. If I simply click the link, I'm taken to a deleted spam post (this obviously requires the 10k+ privilege to view deleted posts) but if I open in a background tab, I end up looking at the site's footer when I visit that tab.
I originally thought this was specific to deleted posts, but I have subsequently also experienced it with non-deleted posts such as this link.
When I originally posted this question, out of the maybe five "modified" links I had clicked recently, two exhibited this behavior.
This is on an iPhone 12 Mini running Firefox 116.0 (33174); to open a background tab, long press on a link and select "open in new tab" from the menu (similar to ctrl-click on desktop).