Do the levels that you’re trying to save have a postfix of “_Auto1”? If so, you don’t have to save them. The engine is trying to fix the failed save level and treat it as a new level. If you can save the current level then you can just uncheck those with “_Auto” postfixes when you’re saving.
This is not a bug but rather a way that the Unreal Engine tries to save your data if you can’t save the current level that you are working with. Sometimes a simple reference mistake can cause an error preventing you from saving it.