Cache invalidation: The locket was cached but later substituted, resulting in stale information. Furthermore, a layer of indirection would ultimately conceal critical updates to the assumed ownership of a certain principal object.

Naming things: He wanted to live forever, but stuck himself with a name he invented as a teenager, and later banned its pronunciation. Also, another of the principal objects had a highly misleading name that tricked both the one who first received it and others later.

Off by one errors: u/chuckleslord@lemmy.world got it right, the auspicious number was spoilt by careless dilution. Meanwhile, the bearer of the third symbol escaped doom at his pleasure and contributed many an off-by-one (or two, or three) error to the occupancy of various rooms in the future.