bricked it this way
Hi, tried that with K420N, Android 6.0. LGUP connected just fine, started flashing the KDZ file, got stuck at step lap (LGUP 13%, phone 0%) for hours. I know I should not disconnect, but it was obviously not going to change any more. Situation now is softbrick, very short boot loop with "secure booting error! error code: 1003". Will not react to POWER + Vol Dwn or Vol up, regardless of when connecting USB. USBdeview or device manager show no connected devices. LGUP can't find phone.
Edit: Line no does change, i.e.
1150 ... secure booting error! (normally)
4360 ... secure booting error! (POWER+Vol Dwn), also takes longer to appear on screen