Benelli Issue?

I bought a Benelli Competiton 12 ga maybe 15 years ago (new equivalent would be a
Legacy) I've shot everything in it from heavy mags to light target loads...100s of rounds. It has never failed until recently. During a recent dove shoot it would fire and eject, but not load the next round. I took it home and thoroughly cleaned it and was ashamed at how dirty I had allowed it to get. So, I figured that was the problem. Took it out again for doves and it cycled perfectly for the first 10 shots. Then started failing to cycle again. A friend came over and we broke it down, cleaned a little more gunk out of it (not much) and neither of us could see any obvious problems. In fact, everything looks very good internally. Have any of you had this problem? Suggestions about solutions? Tom

As Indicated in my OP I have shot everything from maximum load #4 Bismuth to Light trap loads and, until just recently, everyone of them worked just fine. It shoots and ejects the spent shell. The next round slides out of the magazine and remains in the breech. It will not rise to be chambered by the bolt when it closes. The bolt closes all the way, but doesn't pick up the next round. At first i wondered if the round I was shooting was too light to completely activate the unloading/loading exchange until I realized that it has always shot everything from 3" steel to very light loads. The second thing I thought was that it was dirty. I was indeed dirty so I cleaned it really well. But, after the cleaning it cycled the first 10 or so rounds, then started failing again.