I don't have a PC (coz we use 240 volt in our country) but I have 4 different DA cum sander machine. 1 of them does vibrate and wobble a lot. It's becoz of the backing plate which is not stable. I use my hand to move it up & down. It will shake up & down (roughly bout 1mm up & down - right & left). And those sander machine can't really change the backing plate, u can only change the velcro plate.

Anyhow I still got 3 machine to use.... Hehehe.
