HELP Slic3r PE question with print  

HELP Slic3r PE question with print

Hello:

I have a couple of questions on Slic3r PE which I started using recently. I am not an expert on the software and this is my first 3D printer and generally I have been rolling without unsolvable issues, but I cannot figure this one out. I downloaded a file from Thingiverse to print, the TUSH spool roller to use on my LACK cabinet. I printed one successfully after slicing with Slic3r PE and had no issues with it.

I decided to duplicate it ( 4 parts for 2 assembled pieces) to print 2 at the same time. I imported it into Slic3r PE and it was off the build plate so I had to separate the parts and move them around but got it working. Made the GCODE and started the print. For some reason, One of the pieces did not fill in and became a grid. Pictures are attached below for reference. I did not do anything on purpose for this to happen, but it did. The print succeeded and I was able to assemble it together, but I am puzzled by why and how it happened...

1. Is this something that happens sometimes or is it a function of the duplication i did?

2. What settings in Slic3r PE would result in this? the item transformed into a grid on 2 of the 8 parts and I have no idea why or how.

3. I did not save the file as an STL before making the GCODE, but I do have the GCODE file if that helps. I cannot seem to find a program other than the GCODE analyzer to review the GCODE, but I would not understand it in any event. Is there a program which I can import a GCODE to and edit it (maybe export an STL??) or once you make a GCODE is that it.

Thanks all for any help