Firefox Already Running When Using Thunderbird

Debian 12 (Linux 6.1.0-21-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.90-1 (2024-05-03) x86_64 GNU/Linux)

>I am starting Firefox from a launcher in XFCE panel where it was placed automatically at installation time. When *Firefox* is running as the default browser and I click on a link in *Thunderbird*, I **always** get the message > Firefox is already running, but is not responding. To use Firefox, you must first close the existing Firefox process, restart your device, or use a different profile. This, as well as other recommended solutions, works but is not sustainable. Having to close Firefox every time before opening a link from an email isn’t practical. Are others experiencing the same issue? What can be done about it? Chromium doesn’t seem to have this problem, at least.