Peter pugger pug mill only pugging ~half the clay in the chamber

I’m a newly hired ceramics teacher trying to learn to operate the pug mill before my kids get here in a weeks time. I watched a video online and it seems like I’m doing everything correctly… filling the chamber completely, pressing all the buttons and switches in the correct order ect. But after one large log the mill seems to stop pugging, when I open the chamber there is still plenty of clay. And that’s after I release the vaccume seal too.

Any idea what’s going on?