I have a problem with my design and I've been having this problem in many designs I've made that is when I mirror something, I get a straight white line in the middle. I'm barely starting with graphic design and illustrator but It's really frustrating. I've tried many methods that I found in this page and they don't work or I can't properly find them. I have illust CC. They way I mirror is I either copy and paste in front, then I see how much is the width of the original and I manually mirror it making the copy in front mirrored with the same width. Or I use the reflect tool (O). With either I get this white line. Sometimes when I'm zooming in it desappears and reappears. I'd appreciate your answers a lot. Thank you! Sorry for my bad English.