If the lines are part of the custom door leaf object, then you would rightly expect them to show for the 2nd door if they work for the first one.
But I am wondering if in the process of mirroring (MUL) and relocating for the 2nd door, the lines are somehow being moved from their original position.
Versions 6.5 to 22
Dell XPS- i7-6700 @ 3.4Ghz, 16GB ram, GeForce GTX 960 (2GB), Windows 10
Dell Precision M6800 - i7 4700MQ @ 2.40GHz, 16GB RAM, AMD FirePro M6100 (2GB), Windows 7 64bit