Just flew a route from YSCB to YSSY and repeatedly am being assigned to contact Christchurch Center. This occurs near AKMIR and clears again once near BOARE.
I have retested after removing FlyTampa’s Sydney Airport, re-flew same issue, removed Navigraph from the sim and this restored the correct assignment being Melbourne Center.
I also experienced a similar condition flying YSSY-NZAA where Melbourne Center was assigned. Given I was a 1000+KM’s from the FIR boundary looks like an error in the data.