The game has been taking my ability to grapple properly away in several matches over the past few days. Instead, my character will act like he's pulling a weapon from his back, waving his arm around.
Edit: I'm pretty sure the game has ignored other commands similarly. During a couple of my combos, the launcher (useless as it is half the time) wouldn't come out. My character just stopped swinging after the second [Square] attack (Minotaur Hammer), and I ultimately missed my chance to kill the enemy.
Not having quite the same issue,
but I have experienced what you're talking about. Especially in training mode, where you're forced to grapple to finish off the AI opponent, my R1 will often bug out at this point and I'll be forced to exit training mode.
On that note: please implement a training mode where the AI warrior doesn't run out of health!