Breaking a craft with Symmetry + Struts - old bug, includes reproduction

[Temeter]

This is about an original craft. I noticed the issue in a rather intuitive craft, so it was easy to experiment and recreated the steps leading to the bug. This, or at least the symptoms, are a frustrating isse, which has, including many earlier versions, destroyed some ships i spend up to an hour building without saving.

Most ships with these earlier issues included symmetrically placed parts and struts, so I assume the problems is based on a similar behaviour.

KSP Version: v1.0.2.842 Windows 64-bit

Bug, or similar symptoms, were found in versions reaching at least as as far as 0.23, probably older. As for my PC, that was before a hardware wipe.

Mods / Add-Ons: All Stock

Steps to Replicate: I picked parts unrelated to the craft I identified the original issue, and all parts can be interchanged. For simplicity, I restrict myself to a Modular Girder Segment XL and struts (not that it got simpler with all the girders, so I numbered them). This works in a new vanilla save, issue occurs regardless of gamemode:

1) Go into VAB, I used radial angle snap in all cases (not sure if matters).

2) Use a Modular Girder Segment XL (1) as central core.

3) Radially place another single Girder XL (2).

4) Now radially place two Girder XLs on Girder XL (2) using radial simmetry.

5) Do the same with two struts, connecting Girder XL (2) with it's radial Girders.

6) Now pick up and place Girder XL (2) back to Girder XL (1), this time in symmetry. Sometimes 2-times symmetry does not creat the bug, higher symmetry counts are more reliable.

The debug log shows a NullReferenceException when it is reproduced.

Edit: This can be done with placing a single girder and strut in step 4 and 5.

What Happens:

Now the bugged part can't be placed. Putting the greyed out part besides the craft starts their obvious bugged behaviour: These parts can be clicked, but will move the whole ship, so there is no way to remove them. Parts can be placed on them.

This is the simplest version, issues increase when complexity of the situation increase. E.g. instead stacking another Girder XL on the central and reproducing the bug on it instead of the core piece allows you to remove it, including the bugged parts, but sometimes leave their nodes remaining in the VAB, even when starting a new vessel. At times you'll get an infinite spam of null reference exceptions.

Other situations result in actually parts placed where you wanted them, additional to the ghost parts, but often in a variety of bugged states. In some cases this can lead to all buttons in the VAB not reacting anymore, requiring quitting the game via task manager.

Other Notes/Pictures/Log Files:

Picture link (three pics+description, album doesn't for for me):

http://imgur.com/ML6YRJ1,b5q5KLw,VCPFajR#0

Edited May 2, 2015 by Temeter