Message "Tor Browser is already running", when trying to open a link

When the torbrowser is normally running and I try to open another link from another application or from the command line, instead of openning the link in the running instance as it is usually the case for firefox, I can see a separate window with the following message:

Tor Browser is already running, but is not responding. To open a new window, you must first close the existing Tor Browser process, or restart your system.

If I close torbrowser and try to open the link again with closed browser, it opens just fine. But the second link makes the same window.

I found the similar bugreport #12941 (moved), but in that case the window appears when the browser is not running. It's never the case for me.

I use www-client/torbrowser-31.6.0_p450 from torbrowser Gentoo overlay.

Trac:
Username: tot-to