Funny thing is, Onix theke amake bolteo pare nai je mobo asholei 100% thik hoise ki na. They called me saying 'apnar mobo Gigabyte theke pathano hoise. nia jan.' I asked them if Gigabyte repaired the thing or gave me a replacement. They replied 'amra bolte partesi na. apni nia jan. jehetu packet kore ferot pathaise so mone hoy thik hoise'! That's it. They also said that they can't check the mobo because they don't have the right cooler and cpu to check and gave me a 'take your mobo and gtfo, check yourself' look. So i checked it myself and tested everything. Turned out one of the PCI-E slot still not functional.
Since I live very far from IDB, tai eto doura douri korte chachchi na because oikhane jawa amar jonno onek jhamela hoe jay. If the buyer wants, he can claim the warranty again within the remaining warranty period and see if this one issue gets fixed or not.
Already talked to amader vai Vanguard

and i'm pretty sure he's annoyed with my response :/