gpsd.socket file reverts to default

[Rich Wales]

    Ubuntu 20.04 LTS; gpsd 3.20 (installed from the
      Ubuntu package).
      
      I have sometimes found that gpsd is not running.  When I
      investigated, I discovered that the socket file
      (/var/run/gpsd.sock) was owned by root, instead of by gpsd --
      evidently meaning that gpsd would not start because it couldn't
      acquire the socket.
      
      I also determined that the /var/systemd/system/gpsd.socket
      configuration file had reverted to its original default contents:
      
      [Unit]
      Description=GPS (Global Positioning System) Daemon Sockets
      
      [Socket]
      ListenStream=/var/run/gpsd.sock
      ListenStream=[::1]:2947
      ListenStream=127.0.0.1:2947
      # To allow gpsd remote access, start gpsd with the -G option and
      # uncomment the next two lines:
      # ListenStream=[::1]:2947
      # ListenStream=0.0.0.0:2947
      SocketMode=0600
      
      [Install]
      WantedBy=sockets.target
      
      I had previously added the line "SocketUser=gpsd", and also
      commented out the second ListenStream line (since I am not using
      IPv6 on the system in question).  But the original version of the
      configuration file reappeared from somewhere.
      
      This has happened at least twice on this particular computer.
      
      I edited the gpsd.socket file back the way it was previously, did
      "systemctl daemon-reload" to reread the configuration, and removed
      the /var/run/gpsd.sock file, and after doing all this I was able
      to restart the gpsd service.
      
      Any idea what might be going on here, and how I can keep the
      gpsd.socket contents from being reverted?
      
      Rich Wales
      richw@richw.org