Comentário oficial
@Adrian > I expect you also have DVS mode enabled, even if you're not using DVS.
First, please update to rekordbox 5.0.2.
Next, you can check this box and it will fix your problem:

Hello, i have a problem with sync button, when i press it it change bpm but the grid is not synchronise, i must synchronize grid manually by ears, it's no problem but sometimes i must do it fast.... i nedd this,
if i paly on deck 1 and set loop on another track on deck 2 sync button work worst if i synchonize track without loop (normal playing continious)
on version of rekordbxo 4.5 it works fine !!!
somebody help me to solve it.
PS. i can synchronise grid and bmp by ears, but i write earlier sometimes i need to do it very fast and this is not working
@Adrian > I expect you also have DVS mode enabled, even if you're not using DVS.
First, please update to rekordbox 5.0.2.
Next, you can check this box and it will fix your problem:

Publicação fechada para comentários.
I’m having a similar problem with my DDJ-RX. I’ve mentioned it a few times already. When I use the SYNC button, the beats never match. There’s always a small difference. I’ve tried analysing in both modes, I’ve installed all the latest firmware AND rekordbox updates.
But now I saw this item and wanted to try your solution. But I can’t seem to find the tab “DVS” in Preferences???
@Gaetan > If you don't have DVS, you won't see that option.
Please file an inquiry ticket here and our rekordbox support team will be able to gather some additional information to assist you in resolving this issue.