I had something similar happen with my old Daewoo toaster oven, and it turned out to be a simple fix – one of the internal screws had come loose and was rattling. For blenders, you might want to check if the coupling between the motor and the blade is worn out. Also, sometimes food residue gets deep inside and causes resistance. I found the Daewoo manuals here really useful for diagrams and repair steps https://manuals.online/daewoo. They even show how to safely open the base without damaging the casing. Once I followed those instructions, mine was back to working like new. It’s surprising how often these small appliances just need a cleaning or a part tightened instead of a full replacement.