I've been playing Destiny 2 and I notice that I've encountered a glitch. When I went to go change/equip my shaders in my guns and armor, it would not change, and it would not let preview weapons and armor shaders, same thing for armor/weapons mods. Then quickly after that, Ive encountered another glitch where I cant change any of my weapons/armor perks. Also I can't equip ornaments and catalyst. It started a few weeks after Curse of Osiris lunched. And I'm not sure if I'm the only one with this glitch.
Does you controller have any stick drift? If so, that's the most likely cause of your issues. The stick movement interrupts whatever you're trying to do when you press/hold the button.
If you have another controller, try it and see if it works better. If not, try this when the problem happens - rotate both thumb sticks in a circle a couple times, then try to activate the mod/shader/whatever.