I am trying to create a flat pattern for a square to round sheet metal part. I am trying to build a universal design with criteria which will calculate an accurate flat pattern. So far I have a sketch with many sketch relations. The problem I am encountering is when I change a value determining the overall dimensions of the part that the sketch becomes overdefined. I will include my part drawing for references. If I open it up and change the box dimensions from 6inx6in straight to 16inx16in the corresponding flat pattern will rebuild weird. But, if I change the dimensions from 6x6, to 11x11, then to 16x16 it rebuilds fine. I know what Solidworks is doing here and have countered most of the issues regarding that rebuild error.
My real error is in the 3D sketch becoming overdefined when I know it shouldn't. For example: as soon as I try to build the box to 18x18 the sketch becomes overdefined. Although, if I first change the diameter of the round and then set my box dimensions, then return my round diameter to the same number the error does not occur. Hence by using a workaround technique I can obtain the same final dimensions without an overdefined sketch. I'm curious if anybody knows what might be going wrong here and how I might fix it (and avoid this problem in the future). I have already tried to force complete rebuilds. I also did a sketch diagnosis and even when I do nothing sometimes the sketch becomes defined. I did the flat pattern in a 3D sketch because 2D sketch was not easily translating the equal length relation from my other 3D sketch.