I'm wondering if the Elten piece can drop from both Kratuga and Gyfin Rhasia temple (upper) during the event or only from one of them. Wasn't very clear for me in the annoucement. 

As far as I understand the announcement, the part which drops in Hystria Ruins drops during the event in Hystria Ruins, Kratuga, and Gyfin Rhasia Temple (Upper).

Now this was last time, but I would guess it didn't change.  The chart says that only the Crusher can drop the Elten piece, so no Kratuga does not drop the Elten Piece.

Cheers :)