Your links do not describe any problem that is inherent in the principle of such batteries.
They only warn against the danger of not taking care during fabrication to eliminate the moisture from the electrode.
If such low quality electrodes are made, they are prone to decomposition at lower temperatures than the well made electrodes, which have been dried sufficiently.
Similar risks of bad fabrication exist for any kind of batteries, like there were a few notorious cases of lithium-ion battery models that were prone to catch fire.
Moreover, in most applications of such batteries one must use short-circuit protections, so it should be impossible to overheat a battery by shorting its outputs. If that happens, not the battery is guilty, but whoever has designed a device without protections.
The point is that absolutely any kind of battery presents risks. Without short-circuit protections, any battery could cause a fire when shorted.
There is no reason to believe that sodium-ion batteries are less safe than lithium-ion batteries. On the contrary, it is very likely that sodium-ion batteries are safer, e.g. for not having a flammable electrolyte.
