Even the dashboard failed for me, along with every other PAL game.
But I found a workaround! Everything syncs properly if 240p/288p line multiple is set to Line2x, but ONLY Line2x. If it’s Line3x or higher, or Passthru, the 625i signal over VGA fails to sync.
I noticed that even when 240p is set to Line2x, the OSSC seems to initially think the signal is 313p and then quickly switches to 625i.