(Gameplay) Diana unable to cast second ult while using quick cast with indicators

While playing Diana (at least on howling abyss), Diana cannot double cast her ult immediately while using quick cast with indicators. The indicator shows for the spell, but does not cast until another input is used, and then casting the ult again, slowing her combo.

Steps for reproduction:

1. Cast q on a target
2. Cast R on a target marked by q
3. attempt to cast R again. Indicator for the spell shows up, but is orange and will not cast until another input is used, and r is cast again.

Happened to me in two games (one with each skin) on ARAM whenever I would try to double cast my ult.