We had similar issues with early loading tags causing blocking. To help with troubleshooting, I added a query string (i.e. ?tagexclude=alc|bing| or tagexclude=all) exclusion condition where path = \btagexclude\b.*(all|alc\|) to all our vendor tags.  I can select 'all' and exclude all tags from load...

Check the 'Link Tracking' tab and see if the 'Track Outbound Links' checkbox is checked.  We had the same issue some time back and unchecking that was our solution.