I think there is a chance that it is also batch related, some batches have a variance that is not understood, not controlled and has serious consequences. If you hid the VAERs data then there is no way of learning about this.
In the before times, most mRNA related trials were stopped before phase 3 trials because problems with the purification/manufacturing of the mRNA was causing severe injury or death in trial participants.
It is not unreasonable to assume similar problems exist, or that variability/lack-of-control in storage or handling introduce risk.
Also, variability of administration can result in different dose dispersal. For example, if someone is unlucky, more of the vax will enter their bloodstream rather than staying in the muscles. Then it may vary where those lipid nano-particles end up. Wherever they end up, that is the tissue that will be killed by the immune response.