I did some corrections on the antenna part which are in the post above, in the RDM6300-ANT.fzz file, the same changes (adding copper0 and silk screen at least) still need to be done on the RDM6300.fzpz file but I haven't done them (I'll let you practice your skills on that one, feel free to ask for help if you can't figure out how to do it). I also made some corrections to your USB converter module that are in USB converter CP2102_mod.fzpz in the post for that module which are similar to the ones needed here. Those two examples should show you what you need to do to fix up the RDM6300.fzpz file to be correct.
Peter