I've had to turn off the "New filters for edit review" beta feature because it takes so long to load and I can't interact with the page while it's loading. In Firefox, I even get the slow page error which asks me if I want to stop it. With safemode=1, it usually takes about 40-50 seconds for the page to load. If I turn off the Beta Feature, it loads within 5 seconds.
The problem happens in Firefox and Safari, but not Chrome (on MacOS at least). Let me know if you'd like me to debug further.