Rekordbox crashed by transfering playlist to USB, without any Infos in a Log.dat

Hey guys, 

since two weeks i got a hugh problem with my rekordbox sys. 

I will Sync my USB stick with my Mac, so when i go on sync and will transfer my libery the system told me after 40% "there is a problem" and crashed the transfering. After a second run without any chanceings the sys do the transfer complete without a crash. But not all titles are on the stick. more than after the first run but not all. 

I locked the problem in my **house playlist, there is always the crash by transfering my playlist to USB. All others work. 

So rekordbox told me only in a extra Window "An error occurred during export" (picture) put there is no log.dat file.  

could anybody help me with that problem?

Greetz

Pascal