Github vs Gitlab--failure to build/render

I have the strangest issue. It just started last week. I have the a gitlab project. Last week I stopped being able to effectively do a yarn start. It will complain about a “long-running script” after the repo builds and is trying to display. However (and this is the fun part), I checked the exact same files into my work’s github as a new repo and it is working fine. The gitlab repo will still build properly and will build and deploy using codefresh. Also, a coworker working on a mac hasn’t seen the same issues. I get the same behavior across browsers and after clearing browser cache. There are no errors in the browser consoles when this happens. It is just something (NO idea what) that becomes a long-running script that prevents the site from loading properly (after the OAuth authorizes the user and attempts to forward the user to the correct page)–only in the gitlab copy of the repo. Any ideas on how to resolve would be welcome.