First I thought it might be due to my mods, but I get this error with only SML, TFIT and FixClientResourceSinkPoints as well, so I assume that the mods are not the issue.
A set of 2 plugins, one for generating asset dumps from the game and second for making assets from them in editor - GitHub - Th3Fanbus/UEAssetToolkit at rex-dev
Solution
Not to familiar with C++ and/or the asset format, but I seem to have fixed it by adding this to the switch in AkismetBytecodeDisassemblerJson.cpp
case EX_NothingInt32: ReadInt(ScriptIndex); Result->SetStringField(TEXT("Inst"), TEXT("Nothing")); break;
case EX_NothingInt32: ReadInt(ScriptIndex); Result->SetStringField(TEXT("Inst"), TEXT("Nothing")); break;
Will have to see if it messes up with the Asset Generator when it's done dumping