A couple notes on my experience.
I no longer see the splotches on the one that was having the issue. I wished I took a picture right when I did see it. For whatever reason, it disappeared. I know I did do a upgrade to FW17 again and reformat the cards. I was having a issue with the mic button as well on this particular unit. I would turn off the mic, select a different cam view, and the mic would be on again! I turn it off and select the other camera view, mic would be on yet again!
It may be the FW17 that is a little buggy. So far, I found that when and if this happens, I would need to be in park mode, power down the X2 and start it up again. This way, I can more or less be able to keep the mic setting off between switching camera views. Further testing is needed.
Also in general for both of my units, sometimes I find I am driving and the X2 is off. I think the issue is me starting the car too fast. I noticed if I turn the car key too quickly without a pause from park to start, sometimes the X2 doesn't start up. For example, if I parked a long time and the parking time elapsed and turned off the X2 or if perhaps if the X2 turned off due to the voltage setting. Starting the car quickly, the X2 doesn't boot up, leaving me with no recording during my drive. I noticed this a few times. Now I pause a little when I turn the key before starting the car and it seems to take care of that "issue". Again, for this I have to see if it was a coincidence or not.
As far as license plates at night, I noticed it depends on the type of car in front. On my higher up SUV, I can see most plates of other higher cars, such as other SUVs, minivans, and trucks. On lower cars, like sedans, I can't see the plates, as the plates are white from the headlights. This is only based on a small sample of viewing by me tonight. Haven't driven my other car at night, which is lower than the SUV.
