My site is forum.tasat.org, but I’m seeing the same behavior here on Meta, and on forum.obsidian.md.
I can’t pin down anything that consistently precedes a stall, but it seems to be when switching to a significantly different part of a site, e.g. from a topic to admin screen, or to search results.
(Another example was the first time I tried to save this reply. It just spun and spun until I refreshed the page and started over.)
Also: this has now been consistent in Firefox on Windows, Linux, and iOS.