possible bad performance on sharp angles

[Trinitro-Dopamine]

This model perform well in most occasions, however when running with a cube[3], it seems there won't be an enclosure at the angle. I tried with different record method and environment, but therer will always be an angle at the cube which can't be constructed. I did experiment on other rectancular object[2] without sharp angle, it goes well. I wonder if it's because the algorithm or how I use it.

Here is a screenshot during training, I'm sure the missing angle is detected in the images set.

I'm looking forward to hear your reply and tell me if you need and supplementary infomation.