Trying to create a course on generally straight roads but the route planner adds random additions and makes it significantly longer rather than the simple route I’m trying to get it create

I am trying to map simple routes out on the course creator manually but it just seems to add the wrong places, making the route extremely complicated and unrealistic, and simply not what I asked it to do. Makes it extremely difficult to plan long runs. The only way to make it slightly workable is to create mile markers every 50m which I simply can’t do for a 20 mile run