Yeah looks bad. Also for 16' high walls you should be paying a really high premium, especially for level 5. How'd they screw it up they go for the absolute lowest quote and pray? The general contractor or owners should have known better. Anyway it can be fixed but it looks really annoying to do. I guess the entire wall can be rolled with a heavy layer of joint compound, smoothed by hand then sanded, then rolled again and smoothed / flatten by hand then sanded with electric sanders and lights, but you'll need to hire a seriously good finisher. Maybe you can use a very skilled finisher that has a crew who can work with quick set mud do a layer then have them sand and glaze that layer then sand again. A very expencive finisher can probably do the job. Higher the guys who work in billionairs mansions woth a few tens of millions that should do it haha.... Someone with a heavy graco sprayer and a lot of years doing level 5 will be able to fix it too. Anyway stop hiring bottom dollar haha and pay for better materials too. What's that hung with 1/2 inch ultra light?