Charge attack has become random: there are pokemon in which the circle is filled and you can launch it, others that up to 1/3 of the next circle do not launch it, even up to 1/2 of the next circle others.
I tap on the Charged Attack Button at the moment it is full as I have explained, but there are pokémon that launch the attack when is full and others that continue to load always the same level in second circle before launch it.
I think the problem here is the queueing of attacks.
If you spam attacks, like most of us do, you queue an attack during the animation of the prevous attack. I’m not sure but with some really fast quick attacks it might even be possible to queueu another attack.
Try it out, just spam quick moves and then stop. you’ll see your pokemon will do at least one more attack after you stopped.
Since you’ve then queued an attack, if your energy bar fills up the game first need to empty the queue with a normal attack and then can do the charge move.
The combination of fast quick moves and low energy charge move then might give what is described here.