Something to look at - Vcc Turn on time by my HW powering the STSAFE IC to 2.2VDC needs to be 44 uSec. It isn't, mine is closer to 100uSec. Review Table 4 on page 26 of DS13039 Rev 1 for more information. 

I am experiencing a similar issue.  We also have RESET tied to Vcc and the 100nF Cap Vcc to GND and have tried a variety of different "add on" caps to see if we could address the ~10% brick rate.  I sent emails to several people from this chips group...