Cloned Display filter applied to all corrupts view

I had a view with multiple export displays. I cloned a display, replaced the filter (entity form type), applied to all, saved. Applying to all displays was a mistake, I wanted to just apply to this new display. The other displays were already overridden and unaffected, but for one. It's filter got switched too.

But when I tried overriding and changing the filter, pressing apply, no changes were made. I found that I couldn't change the filter in the new display either. Or any of the other displays.

When I tried adding a new filter, I got an AJAX error (500). When I tried cloning a display, I got page not found. When I tried cloning the view, I also got page not found. I tried this with another view and it did not have these problems, so it appears to be limited to the single view.

I solved the problem by importing an earlier version of that view from a staging website. I rebuilt the new display, made sure this time to apply the filter to that display only, without any problem. I found the problem was not repeated when I did so.

This is a nasty one. And hard to categorize. And likely to happen again. If you hadn't heard of this one, it's probably not a Views core issue, but how you implement filters.

I attached the exported corrupted view.