Java Edition:Invalid LastDeathLocation
A player's LastDeathLocation stores the dimension and position that the player last died. It was possible to have the LastDeathLocation tag set to invalid dimensions, or not exist at all when it should.
Obtaining
Missing LastDeathLocation
As players could die before the addition of the LastDeathLocation tag, if the player dies from 13w36a (a 1.7 snapshot) to 22w13a (a 1.19 snapshot), the player will gain a non-zero deaths statistic. Updating to 22w14a and above will of course retain that death statistic, but the player will have an empty LastDeathLocation tag, which is impossible otherwise.
Invalid Dimensions
By dying in any of these April Fools' exclusive dimensions, you could get a LastDeathLocation tag in an invalid dimension.
Moon Dimension
In snapshot 23w13a_or_b, flying above 700 blocks (most likely with the use of an elytra) would teleport the player to the Moon dimension.
Potato Dimension
In snapshot 24w14potato, right-clicking a poisonous potato onto a pedestal would open a portal to the Potato dimension. Pedestals can be found in Ruined Portatoles and villages.
Additional Information
While the tag may be mostly hidden within a player's data, one may check if it is set to a valid dimension by utilizing a recovery compass and checking each dimension. If it does not point to anywhere in the Overworld, Nether, or End, then either the last death location must be set to another dimension, or the player has not died yet in 22w14a or later.
Dying again will remove the old death position, but otherwise it will remain forever.