The Tyros 4 has apparently different issues, although as stated in the previous post the Tyros 4 does not have a ‘drive busy’ issue when recording audio with the indicated USB 3.0 drive. I have not heard of a ‘drive busy’ issue for the USB 1.1 of the S750 either. I hope this remark does not trigger a flood of ‘drive busy’ postings from Tyros 4 and S750 owners

Anyway, this makes me think that recent keyboards have
no internal speed issues with regard to audio recording, although as reported many times on this forum, the S900, S910, S950 do have a compatibility issue with
external USB drives when it comes to audio recording. The writing speed of the external USB drive seems to play a major role in this regard.
I doubt that Yamaha will send compatible USB drives to all owners of the S900, S910, S950, but at least Yamaha could post a list of compatible USB drives (compatible for audio recording purposes, in particular) for these keyboards, along with instructions for use (such as formatting the USB drive on the keyboard, for example, if that has any bearing on the compatibility issue)
(The issue with buying a specimen from a volume production is that one specimen may work, but the next specimen may not work, unless carefully verified for compatibility. This compatibility verification is best done by Yamaha, not by individual users.)