Key for me was to take the console casing apart to expose inside the front panel. Carefully unclipped the ribbon cable than links the sync button and eject button from it’s housing, gave the cable housing a quick dust (could see a strand of dust in it) and re-insert the ribbon cable (fidgety and be careful) and it cured the syncing problem instantly. I did not apply any contact cleaner spray, just a dust with a soft artists paintbrush.
So for me it was a simple ribbon cable dirty or imperfect connection issue. Console is 4 years old.
Result!