Ardour ERROR: Could not set session state from XML [SOLVED]

[Cafe]

Hello,

One of my ardor files got destroyed today, even saving won't restore it. What can I do?
This error message when opening:

Session "/home/user/my_file (snapshot my_file)" did not load successfully:
Cannot initialize session/engine: Invalid or corrupt session state.

---ERROR: Could not set session state from XML
ERROR: Session: cannot create Playlist from XML description.
ERROR: Playlist: cannot create region from XML
ERROR: Session: XMLNode describing a MidiRegion references an unknown source id =91057
ERROR: Session: cannot create Region from XML description. Can not load state for region 'Take14_Cardinal Synth 2-5.2'
ERROR: Session: XMLNode describing a MidiRegion references an unknown source id =91057
...

Is it possible to fix at least the midi data in it?

[Cafe]

Solved

I edited everything in the *ardour file with texteditor

91057

number to

91041

Something might have slipped during the save, the save might have been bad due to double-opened Cardinal windows. I don't know the reason.

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Question:
"what can make an ardour-file corrupt?"