Since they feed fine in the G17 and not the G26, the first thing I’d look at is the magazine spring. They wear out and when they get weak, they do not shove the stack of cartridges up fast enough for the pick-up rail on the slide to feed them. Trying a different, preferably newer, magazine should be the first check. If you are using the G17 mag in the G26, your grip may be putting pressure on the lower portion of the magazine causing an unnatural feed angle.
Second thing, regarding OAL: Use a factory ball round of good feed reliability to set your seating die with the round nose seating stem. (I use M882 NATO ammo for this.) Lock the die settings in place per the ball round. Without changing settings, load a dummy round with the JHP. Cycle it through the pistol by hand and watch for hang-ups. I’ve found, using this technique, the spot on the ogive of the RN bullet which hits the feed ramp will be the same spot on the JHP which hits the feed ramp and causes good feed reliability.