Only in iOS, only in Shipping Mode: Can't find M_SimpleTranslucent

If I package the game in Shipping mode and launch in iOS, I get this warning:

Error: CDO Constructor (CineCameraComponent): Failed to find /Engine/Content/EngineDebugMaterials/M_SimpleTranslucent.M_SimpleTranslucent

If I tap OK, app continues to run without any problem.

But since it is a shipping build, it should not look for EngineDebugMaterials, right?

After working 5 days on this issue, I resolved it but I don’t know how. Probably something that I changed in the project settings, I don’t know at all.