I just opened a ticket with the same problem in Firefox.
I have discovered, however, that if I go to the English subtitles page for our video, and click on the Edit Subtitles button in the upper right, I am taken to the subtitles editor that I cannot get to via "Improve These Subtitles."
By going in through the side door, I was able to make edits and save a new revision. Having changed the version, the problem no longer occurs when working in this video. Testers at Amara may want to consider trying to reload the previous version to see if the problem can be duplicated at their end.
UWMdhhProgram
Hello. We finished subtitling and saved a few videos, but when we try to go back into the file we get this message: A script on this page may be busy, or it may have stopped responding. Has anyone seen this? It's now been 24 hours later.