Base. Data of manifest.rdf could not be read

Windows 11 system with version 24.8.4.2 LO
When I try to open a form in Base I get the error message in the topic title. When I click OK I get the following:-
The Document “Form title” could not be opened
SfxBaseModel::loadFromStorage: 0x70b0f(Error Area:Sw Class:Read Code:15) arg1=styles.xml arg2=0,0

I saw a couple of very old posts with this problem but no solution.

The embedded file containing the form is probably corrupted.
If you upload the file (*.odb), we can give a more accurate diagnosis.

Unfortunately the file is over 4mb.
Some background to what I think may have caused the problem:-

Last time I opened the database my computer was running a little slowly and, in my impatience, I opened the database twice without realising. When I came to close it (no changes made) I was asked if I wanted to save my changes. It was then that I relaised there were two instances of the DB open.
I did save the changes and the problem occurred next time I opened it…
I have a form which opens the data in spreadsheet format and that is still accessible. All other forms have this issue.

Correction: I do have one form (small customer list) which does open OK. All the rest will not open

You have changed from a very old version to 24.8.4.2? Have had the same problem in the past, but this bug had been solved. Might be it has something to do with Tools → Options → Load/Save → General → ODF Format Versions.

Any backup of you Base file? Then try to copy the form from the backup to the current used database file.

No, I update LO regularly. I have backups so I’ll try that.
Thanks