@mfmesa Thanks for your comment, I think there is some kind of malware associated; these chinese rooting apps are free, but they install some unwanted software/daemon which install unwanted software ... without any kind of user control.
I have noticed it suddenly appears installed some apps, for example ShareIt: cc.taosha.toolbox.shareit (/data/app/cc.taosha.toolbox.shareit-1.apk) .
Avast detects shareit as a trojan, and Kinguser (com.kingroot.kinguser) as potentially unwanted
In the 2 android installations where I have been able to replace Kinguser with opensource superuser, the problem is solved, but with the 3rd one I have to investigate: how it downloads and install apps (I have installed AFWall+ and included kinguser in black list), and how to solve the problems in order to replace kinguser. After the tool has done the job of rooting android and kinguser is intalled, kinguser it is no longer a mandatory app.