I liked the post about the quantum fields creating mass. That was a cool point that I hadn't thought of.
There are two possibilities about mass distributions and whether they are detectable outside, and either one creates problems with the laws of physics. Either the information about the mass distribution is destroyed and inaccessible from outside, such that the bobble treats all internal mass as central (like a black hole), or the information about the internal mass distribution is preserved and detectable, such that the bobble itself has non-uniform gravity and moment of inertia. The former option violates conservation of angular momentum during creation and destruction of the bobble, since the angular momentum of an asymmetric rotating mass + bobble system would be instantaneously changed.
Regarding the latter: the last post is arguing that the mass distribution is preserved, which allows you to exchange angular momentum with the bobble eg. by bouncing objects off the sphere obliquely to the center of mass. This means the mass distribution is detectable, either by measurement of rotation change or elsewise by gravity.
Here's how detectability of mass distributions in the bobble breaks the laws of physics. If a bobble is created around objects with initial angular momentum non-symmetric to the bobble, this implies that upon creation the entire bobble must rotate (wobble) about a non-central mass distribution. This means the contents inside are now effectively along for the ride with a wobbling rotation. The book also says you can boost the bobble as a whole to change momentum. So presumably angular momentum can be changed too. Once the bobble ends, that change in (angular) momentum (and energy) must either be distributed among the contents of the bobble or to the region surrounding it. Otherwise it is destroyed, violating conservation of momentum.
It's transferring that momentum upon bobble collapse that creates problems. There is no way to distribute that linear or angular momentum symmetrically in a way that makes physical sense, since the bobble is not supposed to communicate with its contents. If the bobble did transfer momentum to its contents upon destruction you have FTL "timelike" communication within the sphere. Of course such issues are unavoidable during creation. So upon the start and end of the bobble there is a causality violation. Such issues are avoidable at the end of the bobble if that momentum is somehow "stored" on the surface and transferred to the immediate surroundings at the finite speed of light.
If upon collapse the bobble, the contents no longer have the momentum that the bobble contained, but rather that momentum is transferred to the surroundings in some kind of way from the surface, then bobbles would presumably cause an "explosion" once the bobble ends. But what if the net interaction/communication with the bobble is to lose momentum? It's perfectly possible to reduce the momentum of the bobble. That momentum would then have to be transferred into the spherical region when the bobble ends, eg it would have a local "implosion". This would have to imply that information about momentum change is somehow stored on the surface, which can be either positive or negative and must have vector information. There is no way for that information to be stored on the boundary because you can't store information about momentum without it being associated with mass or energy in motion, so this implies that the bobble surface itself has surface-variable energy/mass. Kind of like a freaky scifi holographic principle. OF course we still have the causality violation upon bobble creation.
Violation of causality is just as grievous a physics violation as a conservation law. For example, you can use a bobble to communicate faster than light. Let's say you create one on a light-year scale. It can either have a planet inside the bubble or outside, let's say it's on the boundary and we can control the size just right to either exclude or include it. Since the bobble then has the momentum, angular momentum, and mass of the planet (or not), that information is communicated instantaneously across the bobble surface. This is required since time is stopped inside, the creation of the bobble is automatically "timelike". So you can transfer instantly the planet's momentum to an object a light-year away by bouncing it off the bobble surface. You can also transfer momentum away from a gravitational potential, and mine this to violate the conservation of energy.
What this whole exercise tells us is that there's a deep connection between momentum, angular momentum, and causality. Ordinarily you picture causality as being associated with time, but this perhaps tells us that the real important quantity is spacetime, as we all knew. The universe is held together with such self-consistency that it's amazing how hard it is to poke holes in the laws.
All this says is that these bobble are physically impossible if you start delving into the physics, precisely because this mass distribution issue allows information and momentum to be exchanged with the bobble. If the mass distribution information is not accessible then this violates conservation of angular momentum and other things. If the mass distribution information is accessible this still violates causality and energy conservation.