Quick answer: Unreal SaveGame encrypted in editor failing to load in cooked build? Encryption key derived from project GUID changes per-build - use a stable key from config.

Test save in editor, ship the build. Players can't load their own saves because the key shifted.

Stable key from config

Define encryption key in DefaultGame.ini. Cooked and editor read the same key; saves are portable.

Or disable encryption

For most indie projects, save encryption is over-engineering. Plain JSON with a CRC is sufficient.

Migrate existing saves

If you've shipped encrypted, write a migration that re-encrypts with the new key. Players don't lose progress.

“Encryption keys are infrastructure. They need a stable source.”

Test save round-trip in the cooked build as part of every release. The bug catches itself.