I am noticing that Viacad mating all looked nice and all, but once a part gets out of square with global X/Y/Z, mating won't work anymore, forcing mating with transform and rotate. If it is mathematically difficult to know how to move a part out of square and have former mates still work, I would think we should at least have the option of setting up the workgrid for mating, but even squaring up the work grid first still won't make the mate work.

Once I removed all links from my drawing so that all solids were ACIS solids, then I can align at odd angles. There is something about instant parts with mate/transpose/rotate that seems to confuse the program. It's appearing that the best way to avoid bugs is to remove links after placement. I tried forcing resolve links in case some outdated information was causing the alignment to fail, and I couldn't get it to work. What's even stranger, is the two failed parts that wouldn't mate were already stand-alone ACIS solids, but once ALL parts were converted to stand-alone ACIS solids, then mating at odd angles worked.