My understanding is that the weak point in danger is the neck of a joint pin on either of the connected tracks. With duplo both links have a key pin and a hole.
So when under severe misalignment, one side of the key would be pushed with extra lateral pressure and may deform or break.
However, this sort of severe tension is likely to be in effect while attempting to link/lock the last joint. It's likely to be done by the child when the parent is not there to supervise the feasibility of such forced link. The parent will be alerted when it's either too late or when it succeeded and there's no need to fix it.
Thus, if it were to snap a key neck, then it's just meant to be... No drama. The second key is still there to maintain the joint. Though caution, if no lesson is drawn, such section would become even weaker link!
If it somehow coerced into a loop, then Yay! here comes the locomo. If the train cars don't tip over the forced link gaps or warped sections, then the ride goes on. Otherwise, a tuneup/rebuild is due.
So when under severe misalignment, one side of the key would be pushed with extra lateral pressure and may deform or break.
However, this sort of severe tension is likely to be in effect while attempting to link/lock the last joint. It's likely to be done by the child when the parent is not there to supervise the feasibility of such forced link. The parent will be alerted when it's either too late or when it succeeded and there's no need to fix it.
Thus, if it were to snap a key neck, then it's just meant to be... No drama. The second key is still there to maintain the joint. Though caution, if no lesson is drawn, such section would become even weaker link!
If it somehow coerced into a loop, then Yay! here comes the locomo. If the train cars don't tip over the forced link gaps or warped sections, then the ride goes on. Otherwise, a tuneup/rebuild is due.