Yes, and it works. So does my current solution, which is to change \draw to \path. Either way I have to tinker with the .tex file ROOT gives me, but that’s not so bad. Python regex is easy, and it only has to work for a few months until I graduate ;). Someone who knows these packages better than I do will have to comment on a more robust solution (or if one is even needed – it’s totally possible that the disappearing fills are due to a quirk unique to my setup).