When network connectivity issues prevent any version of InDesign or InCopy from reading from or writing to open files, it performs a protective shutdown. The shutdown can appear to be an application crash or unexpected quit. However, it is intentional behavior to protect from data loss.
Work with your IT department to resolve network connectivity issues. Otherwise, copy files to a local drive before opening with InDesign or InCopy.
The .indd file format is a database, which can be large. So, InDesign (or InCopy) only reads into memory, and writes back to the database, information necessary for the functions currently being performed. This method is a performance optimization that makes working on documents faster than if all of the file data stream was read into memory when opened. When a read or write operation fails, InDesign performs a protective shutdown so that it can call its recovery method to prevent data loss. It stores the data in local memory to a local recovery file in hopes of incorporating the changes into the original file once it is available again. (For more information, see "InDesign document recovery.")
Most other applications use file formats that require the entire file data stream be read into memory when opened, and stored in virtual memory on a local drive. Because all of the data is available locally, a failure to write to the original file can be resolved by prompting the user to save the file in its entirety to an available path.