I checked the snubber bearing – indeed, when turned with a finger it would seize up with a crunching sound. I couldn’t undo the snubber bolt with an ordinary alien key without removing the wheel. So I just sprayed it with a silicon chain lubricant while turning the bearing until no more crunch is heard. The sound has gone. I think I will also add some consistent grease to the bearing. Thank you guys, you’re really helpful as usual!