There's a bug in Volus design that results in the "sprinting" volus having a separate cooldown from the "walking/static" Volus. If you're trying to cloak and it isn't working, switch from whatever you're doing to the other, and you will almost always be able to cloak again.
I'm not sure it's a bug with the Volus. Put a Batarian Gauntlet on any character, and your standing Heavy Melee becomes a Falcon Punch. But your running Heavy Melee is unchanged. It is entirely separate. And of course, KroLord running melee is another example. Running melees are defined for all kits, and the Volus would be no different. They literally would have had to define them individually; e.g.
1-Light Melee
2-Heavy Melee
3-Running "Heavy Melee"
Let's take the Justicar as an example:
1-Light Melee
2-Nova
3-Running Nova
She puts on the Batarian Gauntlet. It redefines her 2-Nova, but her 3-Running Nova is unchanged; she can still do it. Incidentally, this is also what happens when you put the Batarian Gauntlet on the Krogan Soldier. His 3-Running Heavy Melee is unchanged. It does not become a Falcon Punch, but rather inherits the properties of the Batarian Gauntlet, to give his backhand decapitation properties. Now let's look at the Volus:
1-Cloak
2-Shield Bubble
3-Cloak
The Batarian Gauntlet redefines 2, but 1 and 3 are unchanged. And in fact, the Volus does not fit the typical template (2 and 3 being the same; whereas with the Volus 1 and 3 are the same). This is deliberate by design.
Yes I am sure about that. I could never get my Vol enginner to double cloak like that. It always took 5 seconds before it would let me cloak a second time.
I love how, in spite of video evidence, he insists that it is not possible because he can't do it. Oh, BSN.