This is what I have for the latest followers for 357 and the revision date is 1/24/12
Magazine Follower - .357 9-rd, 11-rd, 13-rd, & 15-rd mags only - current follower is marked .357 & 2
From that I would say your magazines have the latest followers. I also think that what you describe as your problem would lead me to suspect a magazine feeding issue.
If it were me and I had any older Gen 3 magazines I would try that in the gun and see what the results were. SJ 40