FWIW, I just got back after ~12h out and about, during which I used my N9 with the PolarCell battery. Happy to say I had no issues with spontaneous reboots or shut-downs, so that does seem to have been fixed by the connector adjustments. The battery was fully charged when I left, and I spent some time browsing the web, checking and replying to emails, one ~10min call, a couple of texts and quite a few snapshots with the camera. Battery was at 77% when I got back - with the old battery (original, 2011) it would have been down to almost nothing. So far so good!