Question about Extruding Connectors
 

Hi, I am a beginner of pointwise.

I am trying to extrude three '2 points curves', which are in the straight line, into a rectangular. I use the similar method described in chapter 3 of tutorial workbook:

1. Select the connectors,
2. create-extrude-translate
3. auto assemble
4. specify the direction and distance

However, if the summation of dimensions of these three lines are below 91, it works well. Once it exceeds 91, the output is very weird, which can be found in attachments.

I also tried:
1. extrude-normal
2. drawing the four edges of rectangular first, then assemble domain
Same output.

Can anyone help me on this?
Thanks!