It flickers in the 1084S because an interlaced picture is sent through your Amiga video output. This is normal.
It doesn't work on your Sony because it's not a 31KHz screen being sent through your BVision. But you can fix that. In the bootmenu, go to System, and set "31KHz default screen". Then save.
Next time you go into bootmenu it will be visible on your Sony monitor.
