Activity Map data is tracked in the next hit after the data has been collected.
In your case:
Click a link in the body
- User clicks the link. --> Activity Map data gets set.
- Custom Link beacon tracks that clicked link. --> Activity Map data is tracked here.
- Next page is loaded and a Pageview beacon tracks that page load. --> Activity Map data has already been sent with the Custom Link beacon, so no Activity Map data is tracked here.
Click a link in the menu
- User clicks the link. --> Activity Map data gets set.
- Next page is loaded and a Pageview beacon tracks that page load. --> Activity Map data is tracked here.