First, welcome to the Nikonians and sorry to hear about the loss of your D600.
"So, the question is: should I or should I not go back to D600?"
If your alternative is another DSLR, that camera will collect dust over time as well. It's about how quickly dust will accumulate and if there is still a lubricant issue. From what I've read, Nikon appeard to have a problem with the shutter mechanism. It shed shutter material on the sensor plus lubricant was being deposited on the sensor. While indications are that these issues have been addresses, the debate and doubt continue for various reasons.
How many of these recent posts are legitimate? Another good question.
In the end you'll simply have to weigh your personal experience with the D600 and it's quality against these posts and decide for yourself.
"Red is gray and yellow white, but we decide which is right ....and which is an illusion"