It has been observed that launching the Gridsync.app bundle on macOS 10.14 Mojave can erroneously result in a "Gridsync is already running error". Normally, this occurs when another, second instance of Gridsync tries to listen on port 52045 but raises a CannotListenError because another, first instance is already listening on this port (in other words, listening on port 52045 is intended to be used as a locking mechanism to prevent multiple instances from running). Unfortunately, CannotListenError is being raised even though, according to netstat -an port 52045 is not listening and, according to ps waux, no other Gridsync processes are running. More investigation is needed to determine why `CannotListenError is raising and/or another locking mechanism needs to be used instead.