I don't recall ever visiting this menu before. But I tried it today and this heppened:
Settings -> Wireless Settings -> Sim & Network Settings -> Click on a sim (SIM 1 or SIM 2, this one is dual sim) -> Scroll to the bottom of the list and click on SIM Toolkit.
This opens up an empty Sim Toolkit menu (which seems to stay empty no matter how long you leave it (tried several minutes)), and when you go Back out of it, you see a couple of new SIM entries have appeared in the list of the current SIM's menu. They each have a checkbox slider thing next to them, but if you tick one slider, in a sec all of them will get ticked.
Does anyone have any ideas about how to proceed with fixing this?
[EDIT] I realised SIM Toolkit is an app. I can force-close it, but I can't seem to be able to clear its data or cache.
[EDIT2] I managed to Freeze it, rebooted, but the existing sim duplicates are not gone.
[UPDATE] Device model: OnePlus 2. Rooted, w xposed framework.
PS: Sorry for the huge image. I assume it only scales horizontally...