Getting RB to remember BPM order on USB playlists

HI All, I'm looking for advice about Rekordbox playlist BPM order. I'm trying to get RB to REMEMBER BPM order in my USB playlists. 

i'm clicking the top of the BPM column to reorder the BPM from low to high, then right clicking the top of the column to Renumber Track Order, but if I restart RB, the machine, or take out the USB, RB forgets the track order and they're jumbled up again. 

Is there a command that I am missing that gets the tracks saved correctly in BPM order so I can turn up at the club with USBs ready to go. 

Many thanks for any help in advance. 

Sam