I think I found the issue in PPM that I was having last week. One of the variables in the characteristic projection was defaulting to zero instead of 1. This also looks like it might be a bug in Athena++ so I opened a PR there, PR #497.
My advisor needed some plots for a talk and I needed them for my committee meeting next week so that’s what I spent most of the week doing; you can find them below. I also prepped my committee meeting presentation except the “Science Goals” section which I will do next. These plots revealed that the accuracy fast magnetosonic wave is only scaling at first order with resolution, not second like it should since we’re using a second order method. I’m not sure why that is yet and haven’t had much luck narrowing down the issue.