When we open the map without first placing property in the ymir work folder, the areadata.txt files will be automatically replace with nothing. The map will be without objects despite the later addition of property. The solution then is to replace the map with the appropriate areadata.txt files.
While gumming textures, the button of this function is pressed. When we change the tool, the eraser button will return to original form, but in fact the eraser function is still activated. This is a tiny bug, but it causes confusion, because until