We have an update,
Thank you for your initial report of this issue. The team is following up to let you know that this bug should be resolved in 26.5. Please update to the latest version of Premiere.
It was found that Opening a Production created with a newer version of Premiere Pro could incorrectly flag it as invalid and overwrite its PRODSET file, and A Production saved in a newer version of Premiere would silently fail to open, when it should have shown an error message.
https://helpx.adobe.com/premiere/desktop/whats-new/release-notes.html
Best,
Amy