It is disheartening to read this response. I would have thought given how widespread this issue is, that your team would be well aware of it. Personally, I have had this issue in the majority of my enclosures. All of the enclosures that experience this issue have natural water that is in reach of the animals. I have had numerous animals dying of thirst while swimming in said natural water, including flamingos and pronghorn.
The crazy thing is this: While you can have animals dying of thirst with natural water in their habitat, adding water (the dripping pipe) immediately fixes the issue. I have seen this in multiple enclosures. When you add the dripping pipe, the animals will immediately drink, but not necessarily from the pipe. They will often start drinking from the natural water when the pipe is added.