Question about Dremel 3000 Series (3000-1/25 SR)

I put the appliance into operation and connected the extension piece because it is easier and more practical to work with. Worked with it for about 15 minutes at level 6 and it worked perfectly. I took a short break of 5 minutes and then continued working on level 6. After about 3 minutes the appliance just switched off. Neither switching it on and off nor changing the socket helped. Have I activated a blocking protection or have I possibly received a defective appliance?