Exception stacking SII mosaic data

Hi

I'm trying to process some data I've taken over the last couple of nights, it's a mosaic, I've selected the options APP wants as it's a mosaic and I've also got drizzle of 0.5 droplets and 2x scaling. The result of my Ha and OIII frames correctly build and I get the fits file at the end. My SII reliably gets an exception trying to write the fits file right at the very end. I've got nearly 900GB of free disk space, so it's got room. I've restarted APP and tried to process just the SII and it still does the same thing. The error message just says an exception occured, with no detail as to what exception, so I have no way to try and correct the problem. The console doesn't have much more information either (other than the last message before failure being "creating FITS HEADER...").

Any way to get any extra logging information so I can try and see what's going wrong?

Thanks