I would say it's broken.
But, seriously the WrpTool forum should be the best place, I would wait for a reply from there.
I know that when this sort of thing happened with WrpEdit it usually meant the file was corrupted in some way, thankfully I was usually able to 'mend' it.
However, WrpTool uses 4WVR format .wrp files and I don't really know how they are laid out as well as I know OPRW.
Maybe the WrpTool people have a nice easy solution for you. ;D ;D
Planck