Basically that message means that one or more files have been damaged.
On one side, the only thing you can do is replace them from the last backup or (if there is none) with files from a new project (that will lose you part of your work).
On the other side, you need to find out why the files were damaged, because only then you can prevent a repeat at a later time. That cause could be a power failure, it could be a cloudsync in the wrong moment (never have your projectfolder autosync in any clouddrive) or a number of other things.
By the way - the project file contains no data and you can replace it from a new project without losing anything. Only if you get other files damaged in addition to that you'll have lostwhat you worked on after your last backup.