Next time you experience lag, there should be something on the microbar (where the button for dungeons and stuff are) that you can mouseover and it will tell you if it’s home or world lag. If your MS for either one is considerably higher (considerably as it’s normal for world MS to be a bit higher than home) then take note. I would refer to this post to troubleshoot.
From what you describe, it sounds like genuine lag. A lot of people call framerate issues lag but it sounds like you’re having actual network issues and not just performance issues.
Also if you’re not living on the east coast or central US, near Chicago where your server is hosted, then your connection will naturally be poorer than if you had a server hosted closer to you.
Sometimes there’s a bug where NPCs won’t react to you because they think they are already talking to you but it doesn’t display on your end. Try moving away from the NPC and then get closer to talk to them again next time this happens, that fixes it for me.