I think you are right about the temperature causing the problem. I read a little from this site:
Although it is about the kefir grains, I imagine it is very related…
It explained that it works best between 68-78 degrees. When it goes below that temperature it is dangerous because other bateria can grow instead of the beneficial bacteria.
I am very sorry about the waste of your goat milk! I might run into the same issue because 68 is about the warmest we keep it in our house and most of the day both of us are gone.
There are heating pads you can purchase for making kefir that keeps the jar (container) a little warmer so that it is within the range needed for it to be successful. I haven’t checked the cost, but might be helpful during the winter months.
I hope your next batch comes out better!