Hi Rodebo,
I was just giving a "for example" and realize it may not fit your situation. However, I find it very interesting that you could see two sets of the wires but not the 3rd since the wires are all produced by the exact same exact object. The telephone pole (both sides) and the two wires are one object placed 3 times each one higher than the previous. Also, the fact that your experience changed when you moved the libraries all suggested a duplicate object (that does not display in P3Dv2) being picked up in some random way (a possibility).
If you are using P3Dv2 and use OZx in some way, read further, otherwise this possibility does not apply to you. If you are using P3Dv2, the fact that one of the three object placements was not seen suggests a duplicate non-P3Dv2 compatible object might have interfered with the rendering of that 3rd instance. That particular telephone pole object is from the AhZx_LIB SUB LibraryFSXP3D. So, the duplicate interference is possible if you have OZx_LIB installed and did not successfully run the Disable OZx mwl, kh, UKVFR et al.cmd utility as required in the AhZx_LIB SUB LibraryFSXP3D installation instructions.
Just an idea, but again it may not apply to you.
Rod