just an update to those who're affected by missing rebates from shopee purchases, i managed to receive the outstanding missing rebates (credited back to my credit card yesterday). not much but it's a start. the CSO who handled my case from start to end called me to say that the bank is working on this gap to avoid the same error again (for missing shopee rebates).
i took it with a pinch of salt as my similar experience with another bank (SC) ended with them cancelling the programme completely (it was about recognising EZ auto-reload with CC). i did make another shopee purchase recently just to test out if what he said is worthy.
so for those who've missing rebates from shopee please don't give up and continue to chase for answer