Flash Drive - Constant Flashing LED, Occaisonally 'Detected'

[random]

I have a drive that was not being detected so I swapped the controller chip (Phison PS2251-03-Q), and it is now giving inconsistent issues.
- Sometimes it will blink once when inserted, then constantly flash
- Sometimes it will blink 3-4 times, 3 times, then constantly flash
- Some of these times it will show the partition in Windows Disk Management, sometimes briefly in R-Studio, sometimes it will show the 'you need to format' pop-up.

If I plug into into a USB tester (USB 2.0 data lines only), it shows 0.02A draw and blinks constantly but around half the speed.

I'm pretty sure it wasn't doing the flashing before swapping the chip.

Will this be a bad NAND chip, or possibly bad controller (purchased from AliExpress), or something else? No shorts, chip is correctly soldered, and everything else seems fine.

This isn't recovery, I'm practising on faulty drives.

Thanks.

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[Lardman]

Will this be a bad NAND chip, or possibly bad controller (purchased from AliExpress), or something else? No shorts, chip is correctly soldered, and everything else seems fine.

Could be any of these. Pull the nand and read externally, if you can't you have your answer, if the controller doesn't drop into safe mode without the nand that also give you something else to work on. Can't comment on the soldering, but it would be the first place I'd be checking - try putting the old controller back and see what you get.

FWIW I would never buy a controller blind like that from AE, especially not for recovery work.