I moved the Lockheed Martin folder into the Program Files (x86) folder (the same folder that contains the Addon Manager folder), started up P3D (v5.1), and the jetways and everything else worked just fine.
Although I can understand why someone might be mislead assuming the "Program Files (x86)" and the "Program Files" folders might be "different", and dedicated to either 32 bit programs and 64 bit programs, these are just conventions, the folders behaves exactly the same and have the same permission sets and, in fact, our software has both 32 bit and 64 bit versions, but the only thing that matters is which executable is being launched, not the folder in which they are installed so, we install them in a single folder to make it easier to update.
What really fixed it in your case, was reinstalling the sim, since I hope with "moved" the LM folder, you mean you uninstalled and reinstalled in the new folder, because just moving the sim folder should never be done, because it would break all the various registry keys which were set on the installation.
So, if you uninstalled/reinstalled it, what really fixed the problem was the reinstallation process, which does further check to be sure all various libraries ( VC++, Simconnect, etc. ) are installed and updated, and it also recompiles the shader cache, which sometimes helps with any graphic problem.
Although nothing in our software requires to install the sim anywhere else than the default folder in C:\Program Files, I personally prefer to install outside of it, C:\Prepar3D V4, or C:\Prepar3D V5. Not because our software requires it, but because OTHER products might have issues, especially those that install inside the simulator folder, which has additional permission locks added by Windows, just because it's located under C:\Program Files ( or x86, it's the same ), since these two are special folders.
So, to be sure I won't be confused by issues caused by add-ons that installs "inside" the sim own folder and need to write there (not allowed by Windows), I always install outside of it, even if our software doesn't have any problems with the default.