It will likely be a stone in there, you would be surprised how many stones turn up in roasted beans. Pop off the grinder adjustment knob, remove the beans container, remove all the screws holding the top cover on. On the models I'm familiar with there are 2 in the front and one at the back down a deep hole under the beans container. Then you can turn the top part of the grinder that adjusts with the knob fully anti clockwise (you may need to click off the bracket that engages the knob) then the top part of the grinding teeth is able to be lifted/levered upwards. By now you should have located the stone, vacuum and brush it out and put it back together.
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It will likely be a stone in there, you would be surprised how many stones turn up in roasted beans. Pop off the grinder adjustment knob, remove the beans container, remove all the screws holding the top cover on. On the models I'm familiar with there are 2 in the front and one at the back down a deep hole under the beans container. Then you can turn the top part of the grinder that adjusts with the knob fully anti clockwise (you may need to click off the bracket that engages the knob) then the top part of the grinding teeth is able to be lifted/levered upwards. By now you should have located the stone, vacuum and brush it out and put it back together.