Xavier PRUYS Great, thanks for the extra details. I think I was able to fix the problem, the transfer for those files should work now.
I also changed it to keep the original extension during transfers. I was setting it to "sty" to increase the compatibility with older keyboards, but I am not sure how effective it is, it's probably doing more harm by breeding same files with different extensions. Let's see first if we stumble upon a keyboard where non-sty extensions are causing problems that needs this measure.
If anyone else stumbles upon any problems with file transfers don't hesitate to report them, the faster we identify the problems the faster we iron them out.
I am also really curious on which keyboards it works, so far I am only aware of successful transfers on Genos and PSR, but I expect it to work on everything going back to Tyros3 at least. So if you have older/more exotic models and it works please let me know too.
Thanks!