Unable to separate by loose parts I am unable to separate all the loose parts of an object which I combined from several objects.

After combining all the objects, I removed doubles.

Now I want to separate the parts again to do some additional editing.

I used the following steps to try to separate the parts


selected the object
tabbed into edit mode
clicked p
clicked on "By loose Parts"
tabbed back into object mode
unselected everything with A
clicked on part I wanted to edit and noticed two other parts  were still connected.


I repeated the process of separating by loose parts, but they will not separate.

How can I disconnect the two side panels?





I have highlighted the faces/vertices, I think might be causing the problem.  When the file is opened they should be visible.  At this stage all the components of the arm assembly are joined.  When separated by loose parts the two side panels stay joined to the main arm.

Is it possible the problem occurs because I extruded the highlighted parts through the two side panels without cutting a hole in them first?

Thank you in advance for any suggestions you may have to help me solve this issue.
Well it's been about a week and with no real help here, I tinkered and finally came up with a solution.  Deleting the connecting vertices between the side panels and the arm.  There were two cylinders I had extruded from the arm through the side panels, which caused the problem.

 

You can test yourself by using the sample file I uploaded here at moonboots  request


tab into object mode
select object 
tab into edit mode
select all faces
click P and select "by loose parts"
tab back to object mode
deselect all
select long arm and notice side panels are still connected
tab into edit mode
using faces select mode, press Alt and LMB to select all faces of first cylinder in the center of the arm.
press Shift-Alt-LMB and select all center faces of 2nd cylinder
press delete button and select vertices
tab into object mode and deselect all
verify side panels have been separated from arm by selecting each item


I now just had a few missing faces that needed to be filled in, but I preserved the location and size of all the pieces so they would fit in the model.  Also I was able to finish the editing I needed to do, to prepare my model for 3D printing.  You can verify how the assembly fits into the total model by clicking on the eye icon next to "frame" in the outliner.