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Here's the response I received from the product team:
The slow response when you turn the record really slow is intentionally designed. As DJs do not want the turntable to respond to hard scratch or large volume sound, the response is intentionally made not too sensitive when turning a vinyl really slow.
You can change this behavior if you select the manual calibration to set an appropriate level of response.
Please see page 20 of the rekordbox dvs setup guide from the link below for how to use the manual calibration.
https://rekordbox.com/_app/files/img/rekordbox_dvs_Setup_Guide_en_b.pdf