@sophieg10675163 ,
I believe now AEP doesn't let the users who already opted out earlier, and they have changed their mind to opt in again, in this case we see an error message in the console, as platform doesn't supporting this feature. It could be a reason for the increase in the bounce rate.
Also, you might need to keep an eye on the number of event calls triggering on the page-load, analytics usually treats the case as engaged but we might be triggering multiple server calls based on business needs.