For the past ~6 months, I have had this issue with UA as well, and also have a hyphenated last name. This past week, I discovered that it is also an issue on Turkish Airlines. I haven’t flown with any other *A partners since the issue started to see if it happens on those carriers as well, but my experience with TK makes me think it’s more widespread than just UA?
I’ll contact AC customer service to make them aware…maybe if more of us complain, it will speed up a fix. It has been very frustrating explaining to every lounge agent while a line forms behind me that I am in fact *G, and that it can’t be added to my boarding pass. I’ve stopped booking UA flights where possible and now take the AC metal on an 014 ticket if there’s an option…maybe this was their ploy all along!?