i don't know what was wrong with the one my client had, i asked him to flip it, he said when i did, the grill was touching the fan and it would break it, i didnt' go into much details with him, just sent him a spare / replacement fan.

if you mean the one i had, yes it probably had bad bearings, i do work a bit with cnc router motor and i know what a bad bearing feels like, it's like you need much less force to spin it with a finger than a fan with a good bearing would. also the center of the rotation was not perfect, aside from the bearing issue it would kinda float up and down when you spin it, you can't see that clear as day but you can feel that it's wiggling while spinning. not sure that makes a lot of sense but i am sure you can get the hang of it.

that fan caused the miner to drift like a fine BMW.