1.8.8 FAWE Schematic Pasting Error

Hello,
I am having this error with FAWE when pasting a schem, this only occurs on my clients server and they are using stellarspigot, is this a spigot error or due to my code.
https://pastebin.com/pPKxHHL2

Code used to paste schem, at the bottom when I #flushQueue is where the error is pointing (it doesn't require any args but for some reason the error comes, it doesn't stop the pasting it just sends the error)

Code (Java):

        World weWorld = new BukkitWorld(spawn.getWorld());
        WorldData worldData = weWorld.getWorldData();
        Clipboard clipboard = null;
        try {
            clipboard = ClipboardFormat.SCHEMATIC.getReader(new FileInputStream(schematic.file)).read(worldData);
        } catch (IOException e) {
            e.printStackTrace();
        }

        EditSession extent = new EditSessionBuilder(weWorld).fastmode(true).build();
        AffineTransform transform = new AffineTransform();

        ForwardExtentCopy copy = new ForwardExtentCopy(clipboard, clipboard.getRegion(), clipboard.getOrigin(), extent, new Vector(spawn.getX(), spawn.getY(), spawn.getZ()));
        if (!transform.isIdentity()) copy.setTransform(transform);

        try {
            Operations.completeLegacy(copy);
        } catch (MaxChangedBlocksException e) {
            e.printStackTrace();
        }
        extent.flushQueue();

 

Does anyone know why this occurs?
I'm really stuck