I noticed that on the nwsp2 classic you can damage the PCB when sliding out the HDD. when it comes from the connector and is pulled backwards it touches the SMD components on the PCB board
Below a screenshot. I already lost two of them (red circles) but was able to solder them back. However that is not easy and risky, better prevent damage.
So when you take out the disk try to lift on the back and slide it backwards very carefully !
I always check for loose "particles" and damage afterwards.