I'm going to come down on the 'sounds like too little' side. My Grandfather played for decades, and his opinion was 'you only have too much when every time you draw the bow, you sneeze from the cloud'

Seriously... bow slipping is either too little, or rosin that's become useless for whatever reason (I understand that leaving it in the sun solidifies it... don't know if it's true, but it sounds good.)

M