Your bit may not be perfectly square to your table. I struggled with this at one time and ended up finding out that I had significant runout in my router spindle to the tune of about .0017" to begin with. I worked on squaring the router to the table and when I thought I had it perfect it was still about .0010". I removed that router and put my normal shop hand held router in and it completely eliminated those kind of lines. It was very frustrating to figure this out and I purchased some new bearings and lower components for the Dewalt DW-611 router to see if I could rebuild it and get it working closer to design but had neck surgery and have not be able to go into the shop.
Get you a cheap dial indicator and stand and order a bit calibration bit from Precise bits or a bit you know isnt bent at all and check the runout. It wont take much runout to see lines like that.