SKHynix PC300 256GB NVMe slow write speed on Windows 10

Whilst testing a fresh install on a Precision 5520, I discovered that the 4k random write speed reported for the 256GB flash drive is a rather poor 2.8MB/sec. As an comparison, a 4k multi threaded speed of 131MB/sec is reported for that drive and a second SSD comes in at over 80MB/sec for 4k random writes.

I have read reports that the Standard Microsoft NVMe driver may be the cause, but there does not appear to be any other storage driver showing as available for this laptop on the Dell support site.

Anyone got any thoughts on whether it's possible to get this back up to expectations?

Cheers.