There are several versions of newer firmware (beta versions) floating around provided by Viofo to beta testers but they are still some bugs that need to get fixed and a few more bugs introduced in the process. If you are not having any other issues other than what you have described, I suggest you stay on that one until a newer stable version is officially launched on the website.
I wish
@viofo could give us a good explanation about the video difference on the rear camera at night compared with the front unit. All I know there are different type of sensors and the rear one is better capable of capturing better detail at lower light conditions than the front unit but don't know the technical details.