Auto constraint showed up today so I've been paying with it. I have a few sketches made from projected geometry that it fails on. but they were pretty complex and took a long time to process, the simple ones have been better and more complex sketches if built gradually and run auto constraint at intervals and it seems to get everything to turn black.
Edit: If I export the sketch to dxf and re import it. I get a fully constrained result as a second choice and the first choice seems the same with some blue details remaining.
