New Numbers update. Some of my numbers when updated cannot be saved

OK, I have found a solution. My file is quite heavy (98MB), so I don't know about yours.

My fix was to go, IMMEDIATELY after opening the file in Numbers, to File > Advanced > Change File Type > Package (it was set to single file).

Since that modification, I'm able to modify and save my file.

I don't know what it changes, or if there's any drawback, but as for know i can work again!

Hope it helps you too.

I have the same problem as you. I have tried the Duplicate option in the File Menu, but i got the same error "The Document could not be autosaved. Your most recent changes might be lost."

I have move the file from iCloud Drive to my Desktop, even to a folder that is not on iCloud, with the same results.

I have restarted Numbers and my computer many times, with no evolution (except that i have indeed lost every change).

I have duplicated the file via Finder, but neither copy is working. In fact, when i open the file, i have a few seconds during which modifications and saving are working, then it's over.

Well, I was wrong... a few moments later, the problem reoccured. So still no solution.