Whenever I drag a guide out, wherever the guide slides along the ruler, the ruler ends up with little black marks along the ruler which makes it difficult to see the actual marks that the ruler has. Any fix for this? Same thing if I just move the mouse around. When you move the mouse, both the top and left ruler follow the cursor with a little line along the ruler so you can see where your mouse is on the page. That little line adds "junk" to the ruler as well. It's only a couple pixels tall of junk, but that makes seeing the 1/8" marks on the ruler difficult to see. Using current CC on OS X.
We are aware of a few drawing issues for the rulers. Your scenario is somewhat similar to those.
Please report a bug for it with more info to reproduce the exact scenario you are seeing at Feature Request/Bug Report Form
As as workaround, create a new document and switch bank to the previous one whenever you see this drawing issue again.
InDesign Engineering Team