Arctic Monkeys sounded fine, the vocals were a bit quiet in the mix early on but that's it.
Axl Rose voice is shot to shit
And Chrissy must have been singing out of tune
I really don't think artists singing out of tune is a technical error unless the sound engineers have some sort of pitch shifter on in the monitor mixes the band hear, which is completely unlikely to be honest. Unless they are using pitch correction like a live auto tune and have a setting to autocorect to notes in specific key and scale but had it set wrong to the song which could happen, but then he didn't really sound like there was any of that, you would clearly hear it.
Another thing to consider is all the bands have their own sound engineers and monitor engineers and everything like that, so it's very unlikely all these top professionals that go all over the world with these bands all get it wrong at the same time. so basically you can put it down to performances and I think the broadcast mix that we're hear is pretty shoddy anywhere, but that's often the case with festival broadcasts.