In the Companion app when using players in the club stockpile for SBC's the players from the SBC storage does not replace the empty space for the specific player. It stays in the storage until it is used as well.
Example: If I send the player Gavi into an SBC from my Club and I have a duplicate untradeable Gavi in my SBC storage the player does not replace the Gavi used. Instead it stays in the SBC storage until it is used from there. It is not possible for me to send the player from SBC storage to the club storage. This issue is also for every player, not only Gavi.