The description of the Paper Bird in the Waterdeep: Dragon Heist adventure (p. 191-192) says:
After you write a message of fifty words or fewer on this magic sheet of parchment and speak a creature’s name, the parchment magically folds into a Tiny paper bird and flies to the recipient whose name you uttered. The recipient must be on the same plane of existence as you, otherwise the bird turns into ash as it takes flight.
The bird is an object that has 1 hit point, an Armor Class of 13, a flying speed of 60 feet, a Dexterity of 16 (+3), and a score of 1 (−5) in all other abilities, and it is immune to poison and psychic damage.
It travels to within 5 feet of its intended recipient by the most direct route, whereupon it turns into a nonmagical and inanimate sheet of parchment that can be unfolded only by the intended recipient. If the bird’s hit points or speed is reduced to 0 or if it is otherwise immobilized, it turns into ash.
There are a couple of things bothering me here. Once it arrives at the intended recipient, the bird becomes "non-magical" but can only be opened by that recipient... If it is no longer magical, then by what force is the bird sealed?
If it is just poorly written and is, in fact, magic that is keeping it sealed, then would a dispel magic spell unseal the bird for anybody, or would it turn the bird to ash? Or would something else happen?