XDJ-RX (1) Problem with double/half sync

Let's say that I play a song with 140 bpm and want to sync a song, let's say 71.5 bpm. When I press sync, the song (71.5bpm) jumps to 140bpm. I would like to have it 70bpm, but it's not working when pressing sync. I have checked the settings and double/half sync is enabled, but it's still not working. Versions of XDJ-RX and rekordbox are the latest. Any help?

Don't wanna hear anything about beatmatching by ear etc. It's not a problem. I just can't understand that XDJ-RX is not doing that while a lot of cheaper DDJ-RB does.

Many thanks!