BiG

I have two MSV25T Bailey de-airing Pug mills. Recently started using one with probably two years of use. No issues until last week, it mixes perfectly the cone 5 Buffalo Wallo soft clay. Issue is, it won't pug forward. It only hums, so I know something is happening in this position of pug. The auger spins and is mixing normal, even the vacuum switch turns on if as if it were to pug. Just before it stopped pugging, it pugged two a large load of clay into complete slabs, so I know there is no blockage. It stopped just short of a full hopper...but still mixes. If I take it apart, what am I looking (specifically) for to troubleshoot?