We’ve fixed this issue in Bricks 1.9.8 beta, now available as a manual download in your account (see changelog).
As with any beta release, please do not use it on a production or live website. It is only meant for testing in a local or staging environment.
@Jargon: Your issue appears more unique, particularly tied to global classes, though it seems to be much worse on your setup. I’ve emailed you some of my observations to further look into it.
@batorbator: Thank you for creating a new thread about global classes. Please discuss any lag related to a large number of classes on this thread: WIP: Builder lags with a large number of classes.
Regarding the elements duplication lag specifically, it is a separate issue we are already aware of. While it gets worse with a larger number of classes, it is a separate concern. We are working on it, but feel free to create a separate forum thread to discuss it, to avoid mixing topics.