Recently I bought a used 6 qt. Kitchen Aid that seemed to be in good condition. It's first test I put it to was to make bagels, which take 73/4 cups flour and 13/4 cups of water. In making the sponge, which takes the first 4 cups of flour, all was well. But when I added 33/4 more cups of flour for the dough, things went south. The Kitchen Aid stalled and eventually stopped. It seemed not to be up to the task of this amount of heavy dough. It just could not knead this amount of dough. Is this to be expected? I took it apart,and the gearbox is good as is, it seems, the rest of the innards. So, is there something wrong with this mixer, or not? Thanks a lot! Ned