DLC parts separate from attachments, sph, vab and world.

[Backslashjack]

All of the DLC parts eventually drift away from their attachment point if they are ever used.

Items on the ends of pistons randomly drifting off of end, Rotors separating and floating meters away from the ship. Hinges sliding away from there attachment points.

[ARS]

This is a common problem for part attachment in KSP, not just for DLC. If G-forces applied on the craft is high enough it could dislocate the parts (sometimes causing it to slam on another part, explosively). An easy fix is autostrutting or put a strut (it's not 100% fixing it, but can minimize the effect)

[Backslashjack]

That is not what is going on here... These parts are not under any extreme stress or anything. and btw pieces have NEVER just moved on me in ksp, ever! Even when they are under extreme stress as you say, and the stress is lifted, the part (if undamaged) will go back to its original position. This is a bug, cut and dried. 

Let me be more clear. In the "VAB" when I simply test stuff with the DLC parts (IE a hangar door going up and down via piston or hinge) parts begin to drift away the more I work on it. Reverting a test from the launchpad will almost certainly result in the DLC parts drifting away from where I originally put them. 

Please help.

[Backslashjack]

[Snip - video of drifting/separating parts in VAB, 1.7.2 Breaking Grounds clean install]

Edited July 6, 2019 by James Kerman
redacted by a moderator

[linuxgurugamer]

Welcome to the wonderful world of floating point math

[Backslashjack]

So everyone knew that this would be an issue with the parts?