Do you have really large hands? I ask because it seems to me that, if you start w/ your left hand index finger up against the underside of the trigger guard, you would have to rotate your hand a bunch to get the meat of your thumb base (have no idea what that is really called) up that high toward the slide. I saw someone doing similar to a glock but it had a small recess left side, just above the trigger guard, that they were pushing down on w/ the end of their thumb. help to absorb recoil. The 92x has an angled extension on the takedown lever to provide a similar effect to that guys glock. But the B92 doesn't have anything there to push on so I am not understanding what you are accomplishing w/ that grip other than messing up a chance to shoot a great pistol. This may show why I can't quite figure how you get this problem.
20190129_085705 by craig stuard, on Flickr