Help With My New Benelli M2

Here's the story:
A few months ago I purchased, brand new, a Benelli M2 Tactical.
I have put about 500 rnds through it.
It ran great with Wally 1-1/8 loads, 2-3/4 regardless of the manufacturer (Remington,Federal, etc.).
The fastest cycling shotgun I ever fired!
Last week it started running sluggish, the shells ejecting almost in slo-mo, occasional FTE.
I scrubbed the chamber, cleaned everything else, lubricated everything.
Still limpy.
I ordered an inertia spring from Brownells ($6, might as well try...), but have not got it yet.
I don't think it should make any difference (or need replacement yet for that matter) but we'll see.
It is a very simple mechanism, no gas rings or anything.
It has an inertia spring, a recoil spring, a firing pin spring and a magazine spring.
One would think it would cycle better with lighter loads as it breaks in but it is quite the opposite.
What can be going on?

Dirty or too dry.

I cleaned and lubed it.
A little better (no FTE) but the shells do not quite eject, more like they fall out ...
They used to shoot out of the ejector port like 6 feet far.

Warranty ???

Ejector in proper working order?

It does eject, but weakly.
It has to do with the speed of the bolt retracting.
If it was a gas operated I would tell you is like if the gas rings have a leak.
As far as warranty goes, they will just tell me that I have to use heavier loads, and that is ok, but why was the gun cycling light loads so well right out of the box and now that is supposedly well broken in it is not?

Try grease instead of oil. My beretta likes grease, will do the exact same thing you described if I use oil.

I remember hearing something about how the Pistol handle stock has something to do with it. Something that it screws up how the inertia system works in the M2 Benelli's I'll try to find a link.

Good call Curtis. I didnt catch that it was a PG Stock.

Check and see if the PG stock is tightened too much or if it has come loose.

Benelli PG stocks are evil.