This error appears when the file size of your save is too large to upload to our servers. To fix this error, reduce the number of saved files you have for that game.
If the issue persists after trimming down the number of saved files, you will need to reach out to us to have our Epic Games store team increase the file size. When you contact Epic Games Player Support please include the following:
Note: Make sure the error code appears and you send us the latest log file generated after this happens.
Let us know how we can help you.