Blurry lines and arrows

Hello. Despite your efforts in correcting this issue, I still seem to have blurry arrows. Here attached a line that looks ok when working but not ok when in preview. One can't even tell if it's a dashed line (it is). 

Any clues?

Hi Melissa,

Thanks for reaching out and sharing what you are experiencing in your project file.

I want to take a look at your project file to investigate what's happening with your permission. You can share it publicly here or send it to me privately by uploading it here. I'll delete it when I'm done troubleshooting.