If the schema specifies that records relate to each other in both directions:

{{
Kitten:
columns:
basket_id: integer
relations:
Basket:
local: basket_id

Basket:
columns:
fluffiest_kitten_id: integer
relaitons:
FluffiestKitten:
type: one
class: Kitten
local: fluffiest_kitten_id
}}

Then a data dump for such a schema won't properly load one of the keys, e.g:

{{
Kitten:
Kitten1:
Basket: Basket1

Basket:
Basket1:
FluffiestKitten: Kitten1
}}

Will result in either fluffiest_kitten_id or basket_id being set to 0

See also ticket DC-555