I don't like to make a thread title in Allcaps, but I think this is a very big problem because of how unobvious it can seem.

If you equip a power armour helmet with the Targetting Hud upgrade, it can make certain NPCs hostile towards you.

This has been confirmed with Paladin Brandis, Kellogg, and the robots at the General Atomics Galleria. I'm assuming it has something to do with NPCs that can converse with you, but can also fight you through either a failed persuasion, or if you choose to initate a fight with the NPC.

This is confirmed for the PS4, but I'm not sure if it occurs on other platforms.

This isn't a game-breaking bug, but it can mean that the player misses out on a lot of story, and potential choices to make in the world.

I'd personally steer clear of the upgrade (even though it is very useful) until this gets patched.

There are other threads which mention this, but I can't post links.