Back in August, I wrote about an issue affecting Panic Button on macOS that occurs if the Panic Button action is set to "Minimize All Windows" and the "Open a new window after all browser windows are minimized" option is selected. More details can be found in this blog post.
Unfortunately, the most recent version of Firefox (version 117 at the time of this post) hasn't fixed the issue. I've investigated further and discovered that this issue is also occurring on Linux (confirmed on Ubuntu 20.04 LTS). The good news is that this issue is not reproducible on Windows, even with the latest Firefox release.
I've opened a bug in Mozilla's Bugzilla database. Until this is resolved, the workaround solution remains the same: users on macOS and Linux should consider turning off the option to open the temporary browser window, or change the Panic Button action to a different selection.