They fixed this i think, in this commit:
https://github.com/EpicGames/UnrealEngine/commit/6b377c8f33d669f64779561d050d141513a44797
Looks good to me!! 
thread on reddit:
If this is fixed in todays update I’m going to be soo happy.
Thought I was going mad, having same issue here. I tried turning off auto manage active camera target, but that turns off my line traces, so hopefully the fix will be out soon.
it looks like it’s fixed in version 4.12.2 Hotfix
Tried to basic scene.
Thanks Epic :o
Double confirm, all fixed here.
The fix put into 4.12.2 will fix most peoples setup, but depending how your pawn is setup you may need another fix that was just put in yesterday (won’t make it till 4.12.3) , or you can download/compile github https://github.com/EpicGames/UnrealEngine/commit/1443cf5b741b669cd8c585c4e379709b35ca730b