Make sure youre are fairly precise with the timing. It should go F1, 1+3, and 4 before the move is over. Same with F1,1+3, DF1 (its DF1 here because you will turn with this move which technically makes it a DB1)
I know some of Geras' moves are dependent on the character hit box of the person youre fighting, but I havent run into an issue landing the kick off that move though.