No, I'm always backing up uncompressed. So I guess it's something on my device that really gets broken. There are already so many little glitches that I'm currently considering doing a complete reflash.

One question about that space-saving reflashing: does it work with own backups only or can I do that magic with official images or with your provided image too? I mean, can I use your image for example to free up disk space and then fill that with my own backup? Or will this occupy the original size again?