Might want to make sure the cable/liner are fully seated in the machine too. I've tripped on the cable before and pulled it out a bit. The larger "gap" quickly caused the wire to bunch up.
For roller tension.. a general rule of thumb is, you should be able to pull the trigger and shoot the wire into a piece of wood.. and the rollers should slip instead of bunching up the wire.
Liners are cheap enough that I replace them about every 6 months.. or if I start having any type of irregular feeding. Although they make liners of different diameters, I've never had any problems shooting .023-.025" wire thru a .035" liner. I just make sure I use the properly sized tip.