Keith Monks Prodigy Plus users, I need some advice

I just picked up a used machine and I cleaned a couple records (that were not important to me). 
To my disappointment the machine left marks on my record near the outer edge. The arm also "chattered" near the end of the record. I don’t know how much use it’s had, but the vacuum tip looked worn, although I don’t know what a new tip looks like. I would assume completely rounded and smooth? 
I played with the suction level and reducing the suction seemed to help as well as tilting the suction tip very slightly, maybe 2 degrees seemed to make it work a little better. 
I used AI #6 one step fluid as well as distilled water. 
I have ordered the Keith Monks discOvery fluid which I hear works best with this machine, as well as replacement tips, but I’m a little afraid to use it on any more records for fear of leaving more marks on the records. 

Any tips for getting this machine to work properly? I did read the manual. 

I’d ad a picture, but am not seeing how to do that.