Python. Indention matters. Unless there is a linter that can tell intent (and maybe there is on that offers an option?) indention can be the difference between once and forever.
It's not just you. I noticed it a few months ago and ended up disabling cursorline entirely. It seems to be caused by an intersection of cursorline and specific syntax highlighting rules (it happens for me in Elixir, but not in Ruby, for example). Honestly, while line highlighting is nice, I can't be bothered figuring out the way through it.