Over the last few days, these are the things that I've tried:
I can enter Fastboot mode and connect to my PC, but can't enter recovery mode.
I was able to unlock my bootloader (I was in the process of waiting for the 360 hours)
I tried flashing fastboot rom with MiFlash, but when MiFlash causes phone to reboot towards the end of flashing, the bootlooping problem occurs again and it cannot complete flashing.
I also tried flashing TWRP from fastboot, it says that it's successful, but when I try fastboot boot twrp.img, the same problem: MI logo and constant reboots.
I also tried to use fastboot oem edl mode and my phone is recognized as Qualcomm device, but MiFlash can't flash in this mode, saying that hello packet is not received.
At this point, I don't know what else to do and wondering if this is a hardware problem. Any ideas?