Some owls do a synchronous tail molt, where they loose all 12 of their tail feathers within a very short time period so they have no tail at all for a while. That’s what Pierce the Barred Owl just did, losing at least four tail feathers yesterday alone.
Barred Owl tail feathers aren’t as stiff and sturdy as, for example, Great Horned Owl tail feathers. An unsupported feather growing in can easily break. If they all grow in together, they support each other.
That must have been the one that shows up as PDF. I’m on mobile rn and will check that out when I’m at home again.