Custom Dataset Bug

[Bill-WangJiLong]

Hello, I use my own data set for training, but there is a strange error during the training process, first of all, both the cano and reposed models lose the mesh below the knee, why is this? And my final result will have some more things, I think this should be caused by the above mistakes, the effect picture is probably like this, how should I modify it? Thanks
cano

reposed

final output