I’ve had it a month now. One time I heard a rattling spring noise with every key press. Volume was off.
I tapped on the bottom of the unit and same noise. I figured there mush be an object laying on the bottom pan so I gently attempted to tilt the board forwards and back to see if I heard it rolling around.
This did seem to change the sound but it was not something loose that I could tell.
I opened up the cover and nothing was loose inside. No objects. I actually thought a key spring had come loose during shipping and was that object I heard.
Then I finger tapped on the cards and there it was the rattling. I pressed the cards back down firmly and some of them appeared to latch back in place (It’s a DIMM socket on the board for each card with a clamping mechanism)
It stopped the noise so somehow I think the clamping mechanism was loose on one or more cards.
Just in case you receive yours or go on a gig and hear something similar to this noise.
The sound was like when you tap on a real spring reverb unit and hear that sound inside.