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 loading or list the ones I want to exclude. You can even do this against production in a web page speed test like webpagetest.org. Of course, the DTM library _satellite rules would still load.