That was exactly what I expected the article to be about, actually. So there is nothing misleading. (Although I expected it to be about their website, not their ticket vending machines. But that's fine.)
I was expecting potential customers to bounce due to some annoying GDPR pop-up that somehow breaks the page.
I think "drop in paper ticket sales" is unlikely to be misconstrued as a drop in sale in general.
Why has this been voted down? The title is plainly trying to imply that it's a confirmed case where the friction introduced by a popup in the purchase flow has seriously damaged sales. "Led to a significant drop" doesn't imply a commensurate rise in non-paper ticket sales, else it wouldn't be written that way. The title is pure clickbait.