Just got my RAS115. My local dealer let me use a demo model to strip some paint and I loved it. So I bought one. I live in a 1920's era house and there are lots of paint stripping tasks that I can do. Anyhow, I'm playing with all of the tool functions (the 30 day clock is ticking) and I can't rotate the green plastic lever on the right side of the dust shroud to remove it. I don't want to force it too much and break it. What am I doing wrong?