There is a technical explanation for this issue of breaking of figures always at the same point (Allow me to put on my uniform of a plastics expert)
When the sprues are molded the molten plastic is pressed with high pressure into the mold - it flows from the injection point filling the cavities and the air is expelled through the slits between the two mold halves. For an ideal molding process both the molten plastic and the mold itself must have a specific temperature (depends on type of plastic, size of mold and channel diameters). Mostly this is determined empirically when starting a molding process.
In each mold the melt advances inside the channels and sometimes two melt front meet at certain points. If the melt at that stage has too low temperature the welding of the two front is inefficient and the resultant sprue (or the figure) will always break at this point.You can check this by observing the "break point" and estimating whether this is linked to the melt paths from the injection point. Just observe the geometry pf the whole thing.
Personally, I have encountered this phenomenon on some sets in the past. Not too often fortunately.
It really is a molding process quality issue.
Hope I didn't club you with this explanation
I've had one set where some of the horses had "torn" legs "Sarmartians" 020...
I suspected this had something to do with the large horse bodies, but whatever the reason their easy too fix by welded them using a temperature controlled soldering iron and trimming off any excess.
I've used this method a lot for alterations, conversions and repairs and it pretty permanent...
practice a bit on scrap sprue/figures to get the hang of it, its best to use small shavings of the same plastic as welding material... pick them up with the tip of the iron and make sure the temp is not so high that the plastic starts to burn... it should just be melting..