Odd sound when turning off and jerky motion

Question

I just bought a refurbished Kirby G6 and it seems to have two potential problems. I've never used a kirby before so I don't know if this is normal or not, but when I turn the vacuum off it makes kind of a loud noise- like something is banging in the brushroll- but there is nothing there. The other problem is that it seems very "jerky". When it is in drive and the propel is going, it seems like you have to push it a little before it will engage and push easier. It creates a very jerky motion. Does anyone have any idea what could be wrong- or is this normal for Kirby vacuums? Thanks