I tried to flash using nefmoto via obd...
I didn't have very good luck flashing over the OBD route my first time. I followed julexs' advice and left the ECU powered down for a full 2 minutes and removed the K-line fuse. I eventually got it to complete 100% after a couple attempts.
I also requested my Nefmoto licence today - having the premium services enabled with shave your 2 min flash times down to under 30 seconds giving it less time or opportunities to error.
Since then, I've only flashed on the bench. With the help of another forum member gathering parts - I built a proper bench flash harness on Friday. So much easier and less worry with getting it out of the car and on the bench. I have never had a flash fail on the bench.