Sandisk Extreme Pro USB 512Gb and 1Tb poor write speeds !?

Having write speed issues with my old Sandisk Extreme Pro 512Gb and brand new 1Tb keys !. Write speed initially around 200Mb/s but quickly drops to 80-100 Mb/s after a three seconds which is unnaceptable. Tried NTFS (4k alloc) and ExFAT (256K alloc) formats to no avail, rebooted PC etc (Windows10). Using a high end Intel PC with fast USB3 ‘SS-10’ port. Source file on a VERY fast M2 drive (around 5Tb/s). Changing drive policy from ‘quick removal’ to ‘better performance’ gives the expected speed boost but only for a few seconds before dropping again to around 80-100Mb/s. Yes latest drivers and Windows updates applied.

What’s happening here Sandisk ?

Your Windows security apps are validating every byte being written to ensure you’re not creating a flash drive to share that is infected with malware.

And never, NEVER, use a journalling drive format on a flash drive. Extra writes, slower speed, reduced drive life span. And yes I’m referring to NTFS. Use FAT32 or exFAT only.