Few comments missing

Hello,
My facebook comments left before June 21st on facebook comment via Ulimate Facebook are not showing up on the website.
I can see them in Facebook Moderation Tool, those missing comments are public.
I tried to re-import comments with no luck. Still missing (for example on that post : http://www.ohmyfood.fr/les-legumes-oublies-a-redecouvrir-au-printemps)
Since June 21st it seems to be ok, all new comments left are displayed.
But i got this issue on older posts :disappointed:
Does someone have an idea of what happened ? Can I fix it ?