Nutball Unswappable Maiden + 4

Nutball Unswappable 

I have uploaded 2 photos of the aftermath of the first few flights of the Nutball, I had a reasonable maiden and 3 other good flights with it but on the 5th flight it suddenly " Nose Dived" and to the right straight into the ground. Is it a characteristic of this type of plane ?as this is the second Nutball I have built and they both seem to want to do this.

The first was slightly larger and made of foamboard not depron as this one.

I would be grateful of any flight info on this, not sure whether to give up on it and try a different scratchbuild.

Please take a look at Photos, sorry no video as yet..