Make sure when you are shaking it you are holding onto the hashin boards themselves as they rattle around in the case like that normally. If you still hear that noise you might have a loose heatsink, if thats the case you do not want to power it up without repairing the board first.
Just saw exactly what was causing the noise : The middle board is loose. What should I do now? Try to repair it locally or send it to bitmain...?