Had this happen again on another room. It was working fine; moved a few objects around and re-export/re-import and something has been corrupted getting the same issue.
I notice that the GMRoomPack.exe complains on the export "Couldn't retrieve contents of room_sect_1:RoomCreationCode.gml", but then it goes on to say "All good!" like the export was successful.
Hello! What would you like to pack? 1 A room 2 All of the rooms 3 Rooms starting with prefix 4 I'm here for the command-line arguments, actually #?: 1 Name the room you'd like to pack! (or paste the full path to .gmx/.yy) Leave blank to go back! > room_sect_1 Where would you like this packed to? 1 To a script 2 To an included file 3 To a GML/JSON file 4 Back #?: 3 File path (.gml for GML format)?: C:\Users\Joiey\Documents\GameMakerStudio2\Santa Run\datafiles\sect1.json Ready to go! Args: C:/Users/Joiey/Documents/GameMakerStudio2/Santa Run/rooms/room_sect_1/room_sect_1.yy C:\Users\Joiey\Documents\GameMakerStudio2\Santa Run\datafiles\sect1.json 1 Go 2 Watch for changes: OFF 3 Readable JSON: OFF 4 Save params for later reuse #?: 1 Couldn't retrieve contents of room_sect_1:RoomCreationCode.gml. Updated C:\Users\Joiey\Documents\GameMakerStudio2\Santa Run\datafiles\sect1.json All good! Press any key to exit!