OK so if this happens, we typically spray some adhesive into the center of the pump to get a bit more friction on the metal rod. This is the adhesive we use, just spray some (~0.5s) at the top while the pump is running, let run until pump returns to full speed. The Khalil Lab has some if you want to borrow from them.
EDIT: I’ve found what works better is spraying the adhesive on a paper napkin and just wiping the the adhesive on the metal rod, with the pump head off, when the metal rod is spinning. This makes sure the adhesive doesn’t prevent the plastic parts of the pumps from working.
