I also stumbled in a bug a few times that when I edit the index of an entry, all the others entries in the page is wiped out. Sometimes it happens, sometimes it doesn't, I'm getting scared to make edits. I just don't know where to report, so I will just paste a few examples here:
@Arthur3921, people have been reporting variations on this problem for several months now. See for example this thread in the Search category: https://community.familysearch.org/en/discussion/150188/index-disappears-from-image-this-image-has-not-been-indexed#latest.
I suggest you go to the relevant index-editor view (such as https://www.familysearch.org/ark:/61903/3:1:939F-KV9B-R2?view=index&personArk=%2Fark%3A%2F61903%2F1%3A1%3A6NVW-F43B&action=view) and use the Feedback tab there to report exactly what you did (who you edited) and what happened as a result. Hopefully if they get enough specific reports like that, they can track down what the heck is going on.
Thank you for letting us know. Our engineers have reported back to me that they are working to correct this issue. Again, thanks for bringing this to our attention.