What is happening is when a jump point is explored there is a random chance of it going to any system. If it is a system that has already been created, surveyed and all existing jump points already lead to another system then the program will create a new jump point. It is perfectly legitimate tactic to resurvey a system if you think a new jump point has been created, especially if you find enemy ships in the system and they didn't come through a known jump point. Mostly what is happening is an artifact of the way the program works.
Brian
So just make up an excuse for immersion's sake and order the resurvey. Will do. There's quite a few on my map, a few in...uncomfortable..positions should they be found by a hostile. My Sol led to two cul de sacs and one nexus system and I think one of the cul de sacs and Proxima, the nexus, have the magenta ring. Proxima already has 6 iirc points, that could make her an even busier system.