I've had two very similar experiences with revolvers that I've owned. In both cases I had the action lightened and discovered, immediately, that I was getting FTFs every fourth or fifth round. The solution was identical in each case, I simply replaced the lightened mainspring with a factory spec. mainspring and the failures to fire were eliminated.
I shoot almost exclusively double action revolvers and, over the years, I've become more and more skeptical about the benefits of trigger jobs. For me, what matters increasingly is not the weight of the trigger pull but its smoothness. And, I've discovered that, with time and a lot of rounds and dryfiring, just about any trigger will smooth out on its own. A couple of years ago I purchased a 66 no-dash that was advertised as unfired. Right out of the box that gun had a fairly rough and heavy trigger. Now, after about 1000 rounds, it has the best trigger of any of my revolvers. I haven't done a thing to it except shoot it. I've had a very similar experience with my 27-3 that I bought in "as new" condition earlier this year. The gun gets lighter and easier shoot with each trip to the range.