Unlike many other readers, I think I know exactly what you're getting at.
Suppose you set up two wormhole ends close to each other with a short offset in time, and then throw a bowling ball into the "future" end. Assuming the wormhole mouths are not imposing special rules (let's suppose it is not turned on yet), nothing prevents you from arranging objects in space, as is normally the case.
Well, "the universe" chose this particular history. That includes natural phenomena and extends to "free will" too since ultimately the metabolism is your brain is physics and natural. One could ask how the universe chose this history over a different possibility. One answer is that it's locally random in every quantum random event with no special rule for larger scales.
This includes entanglement with space-like separated correlated observations, double-slit experiments, etc.
The Novikov self-consistency principle simply applies the exact same thing to spacetime with different topology. The wormhole allows two paths for the quantum wave function, exactly like a double slit, or more precicely, something like a gravitational lensing where paths are different lengths and different enough to be noticable. That's very interesting in itself, in that an interference pattern will show up if you use a narrow enough band-pass filter so the uncertainty in time covers the difference! Point is, what is collapsed and what isn't is not so simple, and context dependent. Delayed choice is also a mind-bending illustration of this.
So, given the arrangement of wormhole and bowling ball, which self-consistent solution (involving time loop) occurs is random with the same rules as anything else: each quantum event is random, but macroscopic events that require a longer chain of quantum events will be rarer because it is a slice of the total probably for the shorter chain.
Consider events A, B, C. For some specific C, you then have a choice of D's. So a specific D is rarer than other C's that end there. Complicated things are rarer than simple things.
Meanwhile, there are rules for random "collapse" (actually, decoherence) which is not, in general, a uniform distribution. Look at a non-local quantum correlation and Bell's Inequalities shows you that some outcomes are more probable. A photon going though a double slit has a higher probability of landing in the bright area of the interference patteren (which is why it's bright after a bunch of photons pass that way).
Now there is another deep principle driving things, known as action. Why does a ball follow Newton's laws? In general why are specific paths strongly preferred, for any phenomena? The interference cancels out most paths except near a maximum, minimum, or saddle point.
So, the richer topology of the wormhole region provides another interference pattern for any particle in the region, and this will impose solutions. This has never been discussed before to my knowledge, but it makes me wonder if there could occur what seems like a force on moving objects, due to this interference.
This should provide food for thought, and fodder for some plausible rules in the story. The people could "tune the interference pattern", "provide a larger pre-existing context for consistency", etc.
Now another thought: the self-interacting bowling ball appears globally as a violation of matter/energy concervation. Perhaps an action principle will invoke itself here, e.g. choosing the solution that minimizes the amount of "extra" energy, momentum, etc. that take place. Maybe it's a kind of information entropy that's minimized, and solutions are preferred which don't change the looping object as much, or minimize observations from the universe at large. You can come up with rules (e.g. momentum) and then as a twist reveal the real rules (e.g. excess momentum which as effects that ultimately spread beyond the time-travel region) which are more subtle.
Maybe the time travelers will find that angular momemtum is prioritized over mass/energy, or momentum non-concervation is minimized but mass itself is not a big deal. They can tune the situation by providing details that involve these variables.
However, you have to ensure that the universe doesn't act on a larger context and minimize excess mass and momentum to zero by not putting the wormholes near each other in the first place. The heros need to work to ensure that the overall context is not strongly not-preferred by the universe. They have to carefully work in stages, "committing" each step by making sure decoherence spreads out over a larger patch of the universe than their subsequent steps will work in. You'll have to fight and outwit Fate to get to the point of doing the experiment! Basically, make it worse not to, and (hand waving) allow "free will" to master these events.
Remember the delayed choice experiment? What seems like a done deal might still be in superposition to some other observer, and he collapses the wave function to a different outcome, erasing your events. In seems that this leads to a multiple worlds model, meaning you can push Fate where you want, but create a parallel universe with your action in it. But, so does any other activity so that can probably be ignored. But playing with that in combination with a wormhole network of FTL travel could make for interesting effects to use in a plot.
My own favorite idea, at least for a story, is that any time you turn on a time machine, something comes out that is part of a loop.