I get an error when I save my blueprint character class which is inherited by the character c++ class I wrote. The same error appears when I save blueprints, my game mode, or umg widgets which for example cast to my character blueprint. Nothing that uses the character class can be saved.
It sounds like a folder permission issue with Windows. Make sure the folders you are trying to save to aren’t set to “Read Only” in Window’s Explorer.
If not, it could be a bad-reference to the C++ class. Did you perhaps move, rename, or something along those lines the C++ class?
I often have a similar error when compiling my C++ Code which is the base for a BlueprintClass (in my case UUserWidget). For me restarting the editor helps (And saving blueprint files before compiling c++ to not lose any progress because I might not be able to save afterwards).
This is due to the “Hot Reload” compiling. Changing Blueprint type code, or variables in C++ causes them to be renamed but not referenced (of some sort) from “VariableName” to “HOTRELOAD_VariableName” which causes referencing errors. A restart fixes those issues, but you can’t save those hot reload references. So it’s best to save, close out of the editor, then do all your C++ changes.
Also, sometimes in your blueprint, hitting File->Refresh All Nodes helps resolve and broken connections from compiling/hotreloading
I rebooted my machine after posting the issue here because rebuilding from source multiple times didn’t work. Rebooting solved it for whatever reason.