Critters that are flying in opened doorways are considered "confined."
This makes them unhappy and glum. I would understand this if the doorway is currently closed, but it even occurs when the doorways are set to open.
I have seen it happen to shine bugs in addition to the dense puftlet in this screenshot as well. (I noticed it as it was the puftlet was sleeping in the doorway.)
I'm not sure if it happens to critters that walk instead of fly.
Steps to Reproduce
Have flying critters. Open some doorways and watch them as the fly through.
Status: Known Issue
We are aware of this issue and have it logged internally but either we do not have a fix ready yet or we are not planning on addressing the issue in the immediate future.