Riven's E randomly disable ?

Just played a match of Definitely-Not-Dominion as Riven and notice that sometimes her E would just be disable after respawn. In order to undisable the E, you would have to get the enemy (not minions) to attack you or sometimes using Q would un-disable it. I don't know if anyone else has the same issue and if it's only on Definitely-Not-Dominion mode or not.