A league memo in April 2016 explicitly cited a review of Caceres’ transfer as the reason for an update to the Player Contract Regulations, introducing a rule that meant loans between sister clubs back to the A-League would not be allowed for two transfer windows after the initial move.
https://aleagues.com.au/news/a-league-transfers-news-sydney-fc-melbourne-city-tickets-details-latest-caceres/So unless things have changed, the Caceres rule should still be in place. But is Auckland classified as a Sister club?
There was also rules with regards to how loans are included in the cap, after Tom Rogic/Victory rorted the cap. Can't recall them exactly atm.