My first thought was summing the angles (each curve piece adds or subtracts 7deg of angle or whatever the actual angle is).
However the question is false in its initial assumption, i think: if theres too much tension anywhere in the string that joint will separate. These pieces are designed to do that.
Perhaps a better way of stating it would've involved the gaps between sections where there might be too much space and lead to derailment.
In the stackexchange thread they say that 12 pieces makes a circle, so each one is 30 degrees, but they also say that you can fit 13 pieces in a "circle", which means that each piece has 30-360/13=2.30 degrees tolerance.
The maximum gap should then be in theory be around 2-3 mm, if this drawing is accurate:
there won't be any added gap (besides the ones due to the tolerance in the interlock), the pieces will deform along their length making no gaps capable of derailing at the juctions.
However the question is false in its initial assumption, i think: if theres too much tension anywhere in the string that joint will separate. These pieces are designed to do that.
Perhaps a better way of stating it would've involved the gaps between sections where there might be too much space and lead to derailment.