If browser freeze happens with activity error popup from pega. Then some rule reference is not correctly provided. You can trace when the section loads and find the error message or private edit of the section and do a trail and error method .
Private edit the section and completely remove everything and keep only a label .
Now If browser still freezes, then there might be an issue outside the section.
Now If browser does not freeze, then there is problem inside the content of section. Now discard the section and take the private edit again and keep only 1 layout at a time and remove others and try.
You can narrow down the layout and narrow down the field which caused the issue.