Hello!
I know this topic has been discussed a few times but no reply was never made that really fixed this problem.
I am using 2 .ods files: one file has a password to open, the other has no password
The file with password “sometimes” cannot be opened again, and the error message shows up. It isn’t possible to repair it automatically, and the XML file doesn’t show any error.
The file without password never bugs
So I tried another software, free ONLYOFFICE. Them both files open normally, I am asked the password to open the passwrd protected file. Same on OpenOffice that I installed for this test
So it seems clear that the problem isn’t in the file itself but in LibreOffice…Therefore all solutions that suggest to check the file, have no incidence at all… And LibreOffice is bugged.
To be able to fix something, there must be a way to reproduce that something first. If you know steps that would e.g. allow me to reproduce it reliably, it would be much more useful to list them in a bug report.
Well, seems that ANY .ods file (I had 4 of them, without macros, all password protected) that generates this error message can be opened in other software, this error has been discussed a few times here and all suggestions ae about a problem in the FILE.
As the file opens in other software we can assume that the problem is not in the file but in Libreoffice.
I will not post here my file as the content is confidential (bank data)).
So, what to reproduce? Take the file, try to open, the error happens. Nothing more.
The usual way:
Make a copy of your file.
Disable track-changes, if you use it.
Replace all letters a-z with x and all digits with 0
Save with password.
Test if error still occurs.
Post for bug-report.
You could guess, that asking the question, I see no problem on my side. So: what to reproduce? People say there is a problem, but don’t share steps to reproduce, only say that I will see it myself if I take the file???; I don’t see a problem → there is no problem.
Not granted. Recently we have introduced some additional checks for file structure, that trigger when the file has some inconsistent pieces of data (ZIP has some redundancy, where different parts of the file contain the same data about files - aimed to help recovery in case of corruption). We now warn and treat such files as corrupt, even when it is technically possible to open them. So it may be still problem with files, just other software doesn’t see it. On the other hand, those files should suggest repairing, and open in repair mode…
Anyway, as I said, no steps to repro for others (no matter how many times people who suffer that problem refuse to share their files) → no problem 
or, in other words: I really want to fix it, but people who actually see the problem need to cooperate.
- Remove all confidential data from the file.
- Save the file, reopen it and make sure the problem remains.
- Upload the problematic file on the forum.