Hello, and thanks for your question! My name is Charles and I am happy to assist you today!!
Sorry for the delay in responce and the lack of knowledge as to the sander in question.
You put your question in the appliance catagory and the tech was confussed as to what it was because Bosch makes appliances also.
I repair and troubleshoot tools all the time and am very familliar with your sander because I am also a contractor and use this same sander to sand down new cabinets.
There are a couple of things that cause this in your sander.
Before we start I need a little info though.
#1, How old is the sander??
#2, was it dropped or damaged at anytime??
#3, How often and hard do you use the sander??
If you still want a refund I will send to customer service.
Looking forward to your reply,