This is an excellent comment. Following this step-by-step guide to the letter will break your screen; it's by far the worst iFixit guide I've seen to date.

100% agree. Step 13-19 are totally unnecessary and just adds the risk of breaking the display connector. “Don’t disassemble stuff that doesn’t need disassembling.” Just ensure there’s no strain on the display cable when removing the battery, i.e. by placing the phone on a non-slippery rubbery surface and fix the display to something sturdy with rubber bands.

To elaborate; When reassembling, the 2.6mm screw needs to go in quite tight, since it squeezes a small rise in the “angled logic board bracket” (really a connector between antenna tuner and the top bezel antenna) against a small gold pad on the main logic board.

This electrical connection needs to work, else the dynamic antenna tuning won’t work - which will cause problems in radio band switching (for instance between 3G and 4G, or different 4G bands). A typical indication that you have a problem here is that it can temporarily be “fixed” by squeezing the top of the phone. It’s really a crappy design choice by Apple.

This is not just a mechanical bracket, but the upper cellular antenna tuning connection to the top bezel antenna. Thus it needs a good electrical connection, or your cell coverage will be bad.

It’s not really a “grounding” bracket, but rather the RF connection to the combined 2.4GHz WiFi/GPS/BT/Diversity cellular antenna integrated in the top bezel. Thus it’s essential that you get a good electrical connection, otherwise your RF stuff won’t work.