all components of .ydd file have to be exported while they are bind to a full skeleton. full skeleton is generally loaded from .yft file and renamed to ".global" > ".skel" in hierarchy. Then the model should be loaded/bind and then it can be exported. Prior exporting, you can switch skeleton to default mode (turn off "Setup mode") and move hand or leg bone to see whether proper geometry moves on .mesh object(s).
Note, some .ydd components use a chopped (non-full) skeleton, e.g lower part uses just a half of skeleton with legs/feet bones only and omits upper torso, hands and head bones completely. as a result, lower part can utilize, say, just 40 bones instead of using skeleton with 200+ bones. this is a game-specific task to drive a copped skeleton using an original full skeleton. but it's your task to export a model using full (200+ bones) skeleton, so correct bones influences are assigned and stored in a model file. otherwise, you have a risk to get legs affected by arms bones or torso/hand bones been affected by head bones or something like this. Always edit model and export when full skeleton is used.