Here's my results after a few hours of playing with navcores (following the tutorials)

I'm running v885 Uk and ROI maps for all:

Navcore 8.410
Initially ok but then becomes a bit erratic - loses sound on POIs, shuts down by itself

Navcore 8.544.1838
Boots into the menu but then locks up until hard reset is performed

Navcore 9.101.516023.2
Gets to splash screen and freezes

Original Navcore 7.903
Runs perfectly - will leave the device like this