Are political disputes a common reason for the uncertainty about timing of the Extraterrestrial Alliance, in carrying out their plans?

This is quite true; it is also the reason for the large variability of events in human history not having a seeming rhyme or reason. You are living in a deadly serious world, on the one hand, because your soul and its safekeeping is at stake, but, on the other hand, it is like an amusement arcade for the extraterrestrial civilizations belonging to that corrupt alliance. They all want to have their innings, they want to take their potshots, they want to exploit various aspects of the human vulnerability and the environment you inhabit. Each civilization has its own history, culture, and bias regarding what it values, what it most enjoys and wants to see happen as well as in the exerting of power personally and culturally. All this goes into the mix. Some are harsher than others. Some are more curious than others, simply wanting to observe. Some want to exploit your genetics for reasons of their own and assist their artificial intelligence robotic beings with a kind of reward by helping them to model after you emotionally, and on and on it goes. Given the somewhat differing priorities, expectations, and goals of the major three competing civilizations of extraterrestrials, there will be somewhat differing tolerance for making way for the others at times to take the lead or have the highest priority for an ongoing operation that might require joint cooperation but serve a more narrow interest of a single civilization than all three combined. This adds to ongoing tension and can stir up rancor with a resulting dissension in the ranks that must be smoothed over. In the meanwhile, this will cause disruptions and a kind of discontinuity even in how things are playing out that might be underway, let alone not yet launched. This is all hidden from human view but will impact their lives.