Your blender has stripped planetary gears.
It's shot. Toast. Too hard to fix.
Why? 1. No easy parts suppliers. 2. Hard to disassemble when the gears are stripped because you can't separate the motor from the gears.
Ninja put in cheap (non-metal) plastic planetary gears in these units. They work ok for most things, but not for ice crushing drinks. While they put the motor mounts on rubber supports, and the drive connection to the base of the blender is rubber, these do not protect the gears from easily being overloaded with the large multi blade pitcher when it is full of cold (hard) ice.
They need to warn people who buy this for ice blended drinks to fill the blender only half full of ice. It's not strong enough to handle a lot of full-pitcher ice drinks.
Mine broke on the fifth pitcher.
They know about this problem, as you only need to search for it in Google. But why is it not fixed? Why is there no recall? Why does Costco carry it in view of their QC policy?
I don't know, but someone should sure get going on this problem I think.