You don't think the core software on which all the other applications and audio engines reside might have something to do with the problems you're experiencing? ;)
Unfortunately Windows 10 does not yet have official support from Pioneer DJ for its products, drivers or software. You can see the full document outlining the Windows 10 verification here.
Until it is officially supported, all I can do is pass your complaint along to the engineers but it likely won't be until later in October that rekordbox is verified and supported and any issues like this have been resolved.