I have 2 that work fine Ted, and I know of many others that do.
My 12 ga. is also an early H&K import and has quite a few flats of shells through it including a bunch of steel.
By 'not returning to battery' what does the malfunction look like?
If the action is all the way closed except for the final rotation of the bolt that's where the drop of oil part comes into play. That's the most common malfunction.
If these get wet, sometimes the stock needs to be pulled and the action return spring cleaned and lubed. The tube that spring runs in can become corroded. That's an easy fix too, the stock comes off easily.
The worst part of the design is the way the trigger assembly pin is held in place. There's a half moon pin/clip thing that hangs around the tube the trigger assembly pin goes through. That half moon (for lack of a better name) clip is easily lost. Then the pin falls out followed by the trigger assembly. Most inconvenient.
Benelli USA was kind enough to send me a replacement and a spare when my trigger fell out on the skeet field. Once you know to watch out for that when you remove the trigger for maintenance it's no big deal, but it's a mickey mouse feature on an otherwise excellent design and I'm surprised to find such a thing on a military derived sporting gun.
You're a smart guy, Ted.... Get the thing to run.
I bet you can.
