I've been breeding horses for some time now, trying to get the best possible horse.
On this long journey I encountered multiple bugs having to do with the horse's health, but what struck me as particularly weird is how random the health of bred horses can be, in contrast to the mostly static jump height and speed.

I've been collecting the data from all my horses, and contrasted it with the current understanding that I have of horse breeding (stats = avg[parent1; parent2; random parent] ).

The random parents' stats seem mostly plausible, although very strange, except for the health. There are multiple cases of out of bounds health stats (I'm talking negative numbers), which according to my understanding of the mechanics should definitely not be possible.

Here you can have a look at the stat table