First, I'm not sure I understand the fault. Is it bordering that turns into a tile? If so..
1. You probably already double checked this but make sure you are using the itemid thats in your obj builder.
2. Download and use Visual Studio Code. Use k+o and select the folder where all your OT/data files exist in and search for the itemId, everywhere that ID is used will popup, simply check through the script. There might be something not intended to use that ID somewhere. You could do the same with the sources but I do not believe anything would popup in there.
Otherwise please provide a video/gif instead.