In speaking with Eric today, I think that I have sometimes relaxed my grip at times and caused a FTE or FTF and then when being CERTAIN to have a very strong grip... found no problems at all.
For some people, in my experience, the grip is not as critcal as it is for me. I am using a grip exerciser daily to make certain of a CRUSH grip on my Rohrbaugh and my many other small and powerful pistols.
To give an idea, on my cheap bathroom scale, I can squeeze 180 lb. with my right hand and 155 with my left. When I was a farm boy, I could always squeeze a bit more than my weight, several times in a row and hold that ammount for quite a while... Since I weigh 230 lb. now, I have begun a squeeze campaign to get up to 230 and hold it there for at least 30 seconds... with either hand but first my right.
I use a two hand crush grip and for me that is what I find it takes to get the failures totally corrected in my tiny and powerful pistols.
I have a .357 Sig in Keltec, the K-P3AT, several tiny pistols in 9x18 which shoot the Wolf 120 gr. at 1100-1250, Walther TPH with QuikShoks, etc. I love small powerful pistols! Rohrbaugh is the smallest and most powerful and thus the most critcal of "slackened grip syndrome" for me.
Slack grip is not a problem on the same pistols for my son and he does not grip them nearly as tightly as I do... I have a theory that there are other factors involved, such as; muscle-skeletal features, exact grip and hold, and the way the pistol and body work together. My son and I shoot a lot of the same guns and they shoot differently for each of us, with no other explanation...
Try a Crush-Grip, two handed grip and see if that cures it.
I seldom if ever have a problem with my P3ATs, nor does my son.
I hope some of this experience and speculation helps.