Looks like a bug that I can't seem to repro. Smudge has been a bit problematic for some users in other ways though (like it doesn't smudge properly and adds like a burn effect when smudging).
Does it help to draw with a lowered opacity?
No it doesn't seem to do anything.
I should notice I'm using the app version that comes preinstalled on my Galaxy Note 10.1. I don't think it make any difference, though. And the app version is 1.41.