You are incorrect. Earthbend's delayed trigger can return the land from exile or the graveyard only if that is the first zone it went to. Any zone change after that but before the return resolves, and the delayed trigger loses track of the card, and can't return it. Doesn't mater if that second new zone is exile or the graveyard. If the land is not in the graveyard or exile for the entire time until the return trigger resolves, it cannot be returned. Those are the rules of Magic, not a bug.

603.6. Trigger events that involve objects changing zones are called “zone-change triggers.” Many
abilities with zone-change triggers attempt to do something to that object after it changes zones.
During resolution, these abilities look for the object in the zone that it moved to. If the object is
unable to be found in the zone it went to, the part of the ability attempting to do something to the
object will fail to do anything. The ability could be unable to find the object because the object
never entered the specified zone, because it left the zone before the ability resolved, or because it is
in a zone that is hidden from a player, such as a library or an opponent’s hand. (This rule applies
even if the object leaves the zone and returns again before the ability resolves.) The most common
zone-change triggers are enters-the-battlefield triggers and leaves-the-battlefield triggers.

603.6c Leaves-the-battlefield abilities trigger when a permanent moves from the battlefield to
another zone, or when a phased-in permanent leaves the game because its owner leaves the
game. These are written as, but aren’t limited to, “When [this object] leaves the battlefield, . . .”
or “Whenever [something] is put into a graveyard from the battlefield, . . . .” (See also rule
603.10.) An ability that attempts to do something to the card that left the battlefield checks for it
only in the first zone that it went to. An ability that triggers when a card is put into a certain
zone “from anywhere” is never treated as a leaves-the-battlefield ability, even if an object is put
into that zone from the battlefield.