Attempting to go to the entity definition from an entity name, for example from within an architecture definition, as below
architecture arch_name of entity_name is
goes instead, either to the architecture line itself, or if the entity has multiple architectures then potentially to a different architecture. This also happens when selecting the entity name from the entity declaration itself.
This is a particular irritation for entities that have multiple architectures, especially where these elements may all be in separate files.