Unaddressed, it compounds into frustration.
And frustration is the soul killer, the destroyer of worker and customer relationships, loyalty and progress.
The solution is pretty simple: address the unhappiness. Change the system or talk about the problem or acknowledge it if that's all that can be done. None of this can happen, though, unless there's communication.
Most open door policies are window dressing. Most, "is everything okay with your dinner?" is rote. True communication, actual intention (and action) in digging deeper, is difficult work. If it doesn't feel like you're working at it, you're probably not doing it right.