What the message is saying is the distance relationship between start and end point do not match the I & J's of your arc's R value. So, what you will have to do is calculate your arc point to both so that the the I's & J's are in proper relationship to your R value. This is what keeps the arc the same distance from center of arc all the way through the arc. It is easier done than said ! Just get out your calculator and crunch some numbers and it won't take long and you will know what I am trying to say here.