An interruption of the connection between MAXQDA and the storage location of the project file can lead to inconsistencies of the database structure of project files. You can find more information about this in our FAQ about saving and opening project files
From Version 2020.1, MAXQDA checks project files for database inconsistencies each time a project file is being opened. If a database inconsistency is detected, you can automatically rebuild the database structure of the project file.
MAXQDA saves a backup copy of the project file to the automatic backup folder before it is being rebuilt. After successfully rebuilding your project database, MAXQDA opens the project file with the rebuilt database structure and you can continue working.
We strongly recommend rebuilding the database structure or use the latest backup copy of the file as working with inconsistent databases can lead to issues with the project file.