Check your resolution setting in your comp window. I bet it's set to something other than full. There is a bug in CC 2017 where it sends the comp panel resolution instead of the full comp resolution. Set it to full, save, and things should be good.
It's on the known bugs list.
Tanks so much! My comp resolution was set to half
No problem! Glad to help.
I was kind of hoping this bug would be fixed in the update that came out a couple of nights ago, but the bugs they fixed in it were much worse (crashing, etc.), so I can understand them not having enough time to fix this just somewhat annoying issue that has an easy workaround! I'd be willing to bet it'll be solved in the next update whenever it comes out.
Sorry about the spelling in this post. I guess I just didn't notice it! I meant to say thanks!