Shimano Spirex 1000 Question

[fishfinderphd]

Does anyone out there fish a newer model (2007 or 2008) of the Shimano Spirex 1000 reel? I bought one about 4 months ago and fish it often. I use 4 lb or 6 lb test on seperate spools. I noticed that whenever I fish baits heavier than 3/8 oz. the reel vibrates and almost feels like it is grinding. Typically I don't fish baits that large on this reel anyway, but there are a few that fit the bill.

I have taken it apart twice lubed everything, check all the gears, springs, etc. and everything looks fine. The teeth on the rotor all seem to be aligned properly. I have no clue why it acts the way it does. So I was wondering if people think this is a defect or simply due to the size of the small reel pulling a "heavy" bait? Thanks!