Hello Caleb,
LSPREPOST represents the AMMGs via their volume fractions. At the corner, it will reconstruct the interface, in this case, with roughly a 45 deg slanted plane. It is just an artifact. It is not wrong. The finer the mesh the smaller this gap is. If you are curious, look "Young's modified Interface reconstruction methods". It is very tricky and complex. But it does the job.
Regards,
Ian Do
You are navigating away from the AIS Discovery experience