I would like to add my tip,
there are casino companies that have many brands once the player comes a VIP, they can easily transmit the player to their other brand and you can say goodbye to your affiliate tracking ID.
yet, some affiliate software's are built to track all the brands of the casino, and some affiliates softwares will not track your player on all brands (technically it's not always possible).... and easily with one phone call to the player they can recommend him to try another brand.
you might have not control over this, but at least you can ask to see if the affiliate software supports this feature....
Good luck!