Mr. Hilmi, CRC errors are usually caused by another problem with the computer (There can be many reasons such as hard disk corruption, power failure while recording, shutting down the computer without shutdown, virus, other general windows problems). Every time ideCAD saves a project, it adds a signature to the file that shows the contents of the project digitally. The reason for the CRC error is that ideCAD found the file in a different state (changed/shrunk) than when it was saved. The second reason, although less common, is that ideCAD is closed before it finishes saving the file. In this case, the project file can only be saved halfway and cannot be opened. If you send your file to our technical service, we will examine whether it can be recovered. In order to prevent such situations, we strongly recommend working with backups, not to work on a single file all the time, but to save with different file names and most importantly to different media using the save as option. For this job, you can use a USB memory most practically. If you make a different save every 3-4 hours while working on the project, you will lose very little in case of such a deterioration.