Grundig GUFSDTR500HD - So when is the disk full?

Discovered that the Freesat+ box had stopped recording a few days ago. Tried setting up some new recordings and they all failed. The box was telling me I had 16% disk space remaining (or 45 hours of SD). Whatever I tried it just wouldn't record anything else. Deleted a program from the library, now records fine! So when it's 84% full, it behaves like it's 100% full. Yet another bug in the software.

If only Harvard would issue a few software fixes, it could be a really good box.