The Golden Knights released a statement saying they "have become aware of an issue with respect to the [Dadonov] trade" and are consulting with the league office.
Dadonov was traded to Vegas by the Ottawa Senators on July 28, 2021.
The date of the trade is key to the dispute.
The Ducks were supposed to receive a conditional second-round selection in 2023 or 2024 from Vegas as part of the trade, while the Golden Knights were set to acquire AHL defenceman John Moore and the contract of Ryan Kesler, who hasn't played since 2018-19.
Dadonov, 33, has 15 goals and 12 assists in 62 games this season, and 249 points in 397 career games.